1257721 九、發明說明： 【發明所屬之技術領域】 本發明係關於氮化鎵系半導體元件’尤其係關於設置具 有優越的特性及生產性之透光性正極之氮化鎵系化合物半 導體元件。 本申請案請求2004年5月26日所提出日本國特許出願 第2〇〇4- 1 5 6543號爲優先權，此文倂入本文參考。 【先前技術】 近年來用以發出短波長光的發光元件用半導體材料，有 一種GaN系化合物半導體材料受到世人的注目。GaN系化[Technical Field] The present invention relates to a gallium nitride-based semiconductor device, in particular, a gallium nitride-based compound semiconductor device in which a light-transmitting positive electrode having excellent characteristics and productivity is provided. Priority is claimed on Japanese Patent Application No. JP-A No. No. No. No. No. No. [Prior Art] In recent years, a semiconductor material for a light-emitting element for emitting short-wavelength light has attracted attention from the world. GaN system
合物半導體係以藍寳石單結晶及各種氧化物基板或III-V 族化合物作爲基板，而在其上以金屬有機化學氣相生長法 (MOCVD法）或分子束磊晶生長法（MBE法）等所形成 〇The semiconductor is a single crystal of sapphire and various oxide substrates or III-V compounds as a substrate, and thereon is subjected to metal organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE method). Formed by
GaN系化合物半導體材料之特性是向橫方向的電流擴散 小。其原因有可能是存在於磊晶結晶中之由基板向表面穿 通的位錯之存在，但是詳細細節並不清楚。並且，在p型 之GaN系化合物半導體，其電阻率係高於^型之GaN系化 合物半導體之電阻率者，以致只是在其表面積層金屬時， 在P層內的橫向電流之擴散仍然幾乎是無，因此當製成具 有pn接合的LED結構時，則僅會在正極之正下方發光。 因此’ 一向是採取施加電子線照射或高溫退火處理以降 低P層之電阻率來強化電流擴散性之方法。然而，電子線 照射係裝置非常昂貴以致不符合經濟效益。而且晶圓面內 1257721 之均勻處理不易達成。採取高溫之退火處理時，爲使效果 顯著地顯現出則需要900°C以上之製程，但是其時GaN之 結晶結構卻將開始分解，以致有因氮脫離所引起之逆向電 壓特性劣化之顧慮。 此外，也有提案揭示一種作爲正極而在p層上使Ni與 Au各積層約數1 〇 nm並在氧氣氣氛下進行合金化處理，以 促進P層之低電阻化及形成具有透光性與歐姆性之正極之 方法（參閱例如發明專利第2,803，742號公報）。 § 然而，就在氧氣氣氛下之合金化處理而言，將在經露出 的η型GaN層之表面形成氧化物層，以對負極之歐姆性造 成影響。並且經過氧化氣氛合金化處理之Au/Ni電極卻具 有網目結構，以致容易造成發光不均勻性或因機械強度弱 致必須設置保護膜而使製造成本上升。_上由於將Ni在氧 氣氣氛下加以熱處理，N i之氧化物將覆蓋在表面，因此若 在透光性電極上形成焊墊電極時，則其密著性較差以致不 能獲得接合強度。 ® 另外，也有一種提案揭示作爲正極而在p層上形成Pt層 然後在含氧氧氛中進行熱處理，以同時達成p層之低電阻 化與合金化處理之方法（參閱例如日本發明專利特開平第 1 1 - 1 86605 號公報）。 然而，由於該方法也是在氧氣氣氛下進行熱處理，仍有 上述問題存在。而且，以Pt單體如欲獲得良好的透明電極 則必須作成爲相當薄（5 nm或以下），結果使得Pt層之電 阻增局，且即使經由熱處理而達成P t層之低電阻化，電流 1257721 之擴散仍然不佳，以造成不均勻發光且將招致正向電壓（ VF )上昇及發光強度降低之結果。 【發明內容】 爲解決上述問題，本發明之目的係提供一種氮化鎵系化 合物半導體發光元件，其係不再需要電子線照射或高溫退 火或在氧氣氣氛下之合金化熱處理等，且設置具有良好透 光性與低接觸電阻之具有優越的電流擴散性之正極者。在 本發明中所謂「透光性」係意謂對於3 00〜600 nm之波長 區域之光爲透光性。 本發明提供如下之發明。 (1) 一種氮化鎵系化合物半導體發光元件，其特徵爲 其係在基板上將由氮化鎵系化合物半導體所構成 之η型半導體層、發光層及p型半導體層依此順 序積層所構成，且負極及正極係分別接於η型半 導體層及Ρ型半導體層所設置者，且該正極係具 有由至少設置與ρ型半導體層相接之接觸金屬層 ，再在該接觸金屬層上設置導電率爲大於接觸金 屬層者之電流擴散層，並且又在該電流擴散層上 設置接合墊層之三層結構所構成之透光性電極， 且在該Ρ型半導體層之正極側表面包含含有用以 形成接觸金屬層的金屬之正極金屬混雜層。 (2 ) 如第（1 )項之氮化鎵系化合物半導體發光元件， 其中正極金屬混雜層之厚度爲0.1〜10 nm。 (3 ) 如第（1 )或（2 )項之氮化鎵系化合物半導體發 1257721 光元件，其中在正極金屬混雜層用以形成接觸金 屬層之金屬之濃度爲相對於該正極金屬混雜層中 全金屬爲0 · 0 1〜3 0原子％。 (4 ) 如第（1 )〜（3 )項中任一項之氮化鎵系化合物半 導體發光元件，其中在接觸金屬層之P型半導體 層側表面設置含有III族金屬之半導體金屬混雜層 〇 (5 ) 如第（4 )項之氮化鎵系化合物半導體發光元件， 其中半導體金屬混雜層之厚度爲0.1〜2.5 nm。 (6 ) 如第（4 )或（5 )項之氮化鎵系化合物半導體發 光元件，其中在半導體金屬混雜層之III族金屬之 濃度爲相對於該半導體金屬混雜層中全金屬爲0.1 〜5 0原子％。 (7 ) 如第（1 )〜（6 )項中任一項之氮化鎵系化合物半 導體發光元件，其中接觸金屬層爲白金族金屬及 Ag。 (8 ) 如第（1 )〜（7 )項中任一項之氮化鎵系化合物半 導體發光元件，其中接觸金屬層爲白金。 (9 ) 如第（1 )〜（8 )項中任一項之氮化鎵系化合物半 導體發光元件，其中接觸金屬層之厚度爲0.1〜 7.5 nm 〇 (1 0 ) 如第（1 )〜（9 )項中任一項之氮化鎵系化合物半 導體發光元件，其中接觸金屬層之厚度爲5 nm以 下。 1257721 (11) 如第（1 )〜（1 ο )項中任一項之氮化鎵系化合物 半導體發光元件，其中接觸金屬層之厚度爲0.5〜 2.5 nm。 (12) 如第（1 )〜（1 1 )項中任一項之氮化鎵系化合物 半導體發光元件，其中電流擴散層爲選自由金、 銀及銅所構成之族群中之金屬或含有該等金屬中 至少一種之合金。The characteristics of the GaN-based compound semiconductor material are such that the current in the lateral direction is small. The reason for this may be the presence of dislocations which are present in the epitaxial crystal through the substrate to the surface, but the details are not clear. Further, in the p-type GaN-based compound semiconductor, the resistivity is higher than that of the GaN-based compound semiconductor of the type, so that the diffusion of the lateral current in the P layer is almost the case only when the surface layer is metal. No, therefore, when an LED structure having a pn junction is formed, only light is directly emitted under the positive electrode. Therefore, the method of applying electron beam irradiation or high-temperature annealing treatment to reduce the resistivity of the P layer to enhance current diffusivity has been conventionally employed. However, electronic line illumination systems are so expensive that they are not economical. Moreover, uniform processing of 1257721 in the wafer surface is not easy to achieve. In the case of annealing at a high temperature, a process of 900 ° C or more is required to remarkably exhibit the effect, but at this time, the crystal structure of GaN starts to decompose, so that there is a concern that the reverse voltage characteristics due to nitrogen detachment deteriorate. Further, there has been proposed a method in which a Ni and Au layers are laminated on the p layer by about 1 〇 nm as a positive electrode and alloyed in an oxygen atmosphere to promote the low resistance of the P layer and to form light transmittance and ohmicity. A method of the positive electrode (see, for example, Japanese Patent No. 2,803,742). § However, in the alloying treatment under an oxygen atmosphere, an oxide layer is formed on the surface of the exposed n-type GaN layer to affect the ohmicity of the negative electrode. Further, the Au/Ni electrode which has been subjected to an oxidizing atmosphere alloying treatment has a mesh structure, so that it is liable to cause unevenness in light emission or to provide a protective film due to weak mechanical strength, thereby increasing the manufacturing cost. Since Ni is heat-treated under an oxygen atmosphere, the oxide of Ni can be covered on the surface. Therefore, when a pad electrode is formed on the translucent electrode, the adhesion is poor so that the bonding strength cannot be obtained. In addition, there is also a proposal to disclose a Pt layer formed on a p-layer as a positive electrode and then heat-treating in an oxygen-containing oxygen atmosphere to simultaneously achieve a low-resistance and alloying treatment of the p-layer (see, for example, Japanese Patent Publication No. 1st - 1 86605). However, since the method is also heat-treated under an oxygen atmosphere, the above problems still exist. Moreover, if a good transparent electrode is to be obtained with a Pt monomer, it must be made relatively thin (5 nm or less), and as a result, the resistance of the Pt layer is increased, and the resistance of the Pt layer is lowered even by heat treatment. The diffusion of 1257721 is still poor, resulting in uneven illumination and will result in a rise in forward voltage (VF) and a decrease in luminous intensity. SUMMARY OF THE INVENTION In order to solve the above problems, an object of the present invention is to provide a gallium nitride-based compound semiconductor light-emitting device which does not require electron beam irradiation or high-temperature annealing or alloying heat treatment under an oxygen atmosphere, and is provided with A positive electrode having excellent light transmittance and good light transmittance and low contact resistance. In the present invention, "transparency" means that light in a wavelength region of from 300 to 600 nm is translucent. The present invention provides the following invention. (1) A gallium nitride-based compound semiconductor light-emitting device characterized in that an n-type semiconductor layer, a light-emitting layer, and a p-type semiconductor layer composed of a gallium nitride-based compound semiconductor are stacked in this order on a substrate. And the negative electrode and the positive electrode are respectively connected to the n-type semiconductor layer and the germanium-type semiconductor layer, and the positive electrode has a contact metal layer provided at least in contact with the p-type semiconductor layer, and then conductive is disposed on the contact metal layer. a transmissive electrode having a three-layer structure in which a current diffusion layer is larger than a contact metal layer and a bonding layer is provided on the current diffusion layer, and the positive electrode side surface of the germanium semiconductor layer is contained To form a positive metal mixed layer of a metal contacting the metal layer. (2) The gallium nitride-based compound semiconductor light-emitting device according to Item (1), wherein the positive electrode metal mixed layer has a thickness of 0.1 to 10 nm. (3) The gallium nitride-based compound semiconductor according to (1) or (2), wherein the concentration of the metal used to form the contact metal layer in the positive metal mixed layer is relative to the positive metal mixed layer The total metal is 0 · 0 1~3 0 atom%. (4) The gallium nitride-based compound semiconductor light-emitting device according to any one of (1) to (3), wherein a semiconductor metal mixed layer containing a group III metal is provided on a side surface of the P-type semiconductor layer contacting the metal layer. (5) The gallium nitride-based compound semiconductor light-emitting device according to Item (4), wherein the semiconductor metal mixed layer has a thickness of 0.1 to 2.5 nm. (6) The gallium nitride-based compound semiconductor light-emitting device according to item (4) or (5), wherein a concentration of the group III metal in the semiconductor metal mixed layer is 0.1 to 5 with respect to the total metal in the semiconductor metal mixed layer. 0 atom%. (7) The gallium nitride-based compound semiconductor light-emitting device according to any one of (1) to (6) wherein the contact metal layer is a platinum group metal and Ag. (8) The gallium nitride-based compound semiconductor light-emitting device according to any one of (1) to (7) wherein the contact metal layer is platinum. (9) The gallium nitride-based compound semiconductor light-emitting device according to any one of (1) to (8), wherein the thickness of the contact metal layer is 0.1 to 7.5 nm 〇(1 0 ) as in (1) to (1) The gallium nitride-based compound semiconductor light-emitting device according to any one of the preceding claims, wherein the contact metal layer has a thickness of 5 nm or less. The gallium nitride-based compound semiconductor light-emitting device according to any one of the items (1) to (1), wherein the contact metal layer has a thickness of 0.5 to 2.5 nm. The gallium nitride-based compound semiconductor light-emitting device according to any one of the above-mentioned items, wherein the current diffusion layer is a metal selected from the group consisting of gold, silver, and copper or contains the metal. An alloy of at least one of the metals.
(13) 如第（1 )〜（1 2 )項中任一項之氮化鎵系化合物 半導體發光元件，其中電流擴散層爲金。 (14) 如第（1 )〜（1 3 )項中任一項之氮化鎵系化合物 半導體發光元件，其中電流擴散層之厚度爲1〜 2 0 nm 〇 (15) 如第（1 )〜（14 )項中任一項之氮化鎵系化合物 半導體發光元件，其中電流擴散層之厚度爲1〇 nm以下。 (16) 如第（1 )〜（1 5 )項中任一項之氮化鎵系化合物 半導體發光元件，其中電流擴散層之厚度爲3〜6 (17) 如第（1 )〜（1 6 )項中任一項之氮化鎵系化合物 半導體發光元件，其中接合墊層爲由共晶焊錫材 料所構成。 (18) 如第（1 )〜（1 7 )項中任一項之氮化鎵系化合物 半導體發光元件，其中接合墊層爲由Au、Sn、或 含有Au與Sn之3元系焊鍚合金所構成。 1257721 以與p型GaN系化合物半導體之接觸電阻爲低之金屬， 例如以白金族金屬之薄層作爲接觸金屬層，並在其上設置 導電率爲大於接觸金屬層者之電流擴散層的本發明之透光 性正極，其在正極面方向的電流之擴散將受到改善，其結 果即可實現正向電壓（VF値）爲低且會在正極全面均勻發 光之高亮度發光元件之製造。 【實施方式】 〔本發明之最佳實施方式〕 茲參閱圖式就本發明之最佳實施例說明如下。但是本發 明並非僅爲該等實施例所局限者，例如該等實施例之構成 要素彼此可適當地組合。 第1圖係展示具有本發明透光性正極之氮化鎵系化合物 半導體發光元件100之剖面模式圖。 本發明之氮化鎵系化合物半導體發光元件1 00，係在基 板1上隔著緩衝層6而加以形成氮化鎵系化合物半導體層 2，並在其上形成本發明之透光性正極1 0。 氮化鎵系化合物半導體層2係例如由η型半導體層3、 發光層4及ρ型半導體層5所構成之異質接合結構所構成 〇 負極20係形成在η型半導體層3之一部份，透光性之正 極1〇係形成在ρ型半導體層5之一部份。 而且透光性之正極1 0係以接觸金屬層1 1、電流擴散層 12及接合墊層13之三層所構成。 對接觸金屬層1 1所要求之性能，爲與Ρ型半導體層5之 -10- 1257721 接觸電阻必須爲小。並且，在用作爲從電極面側取出來自 發光層4之光的面朝上組裝型發光元件時，則被要求具有 優越的光透過性。 接觸金屬層1 1之材料係從與P層的接觸電阻之觀點來考 量，則較佳爲白金（Pt )、釕（RU )、餓（Os )、铑（Rh )、銥（Ir )、鈀（Pd )等之白金族金屬或銀（Ag )。該 等中Pt係因其功函數（work function )高，且對於末經施 加高溫熱處理的比較高電阻之P型GaN系化合物半導體層 § 是可在非加熱下獲得良好歐姆接觸，因此爲特佳。 若以白金族金屬構成接觸金屬層1 1時，則從光透過性之 觀點來考量，則必須使其厚度作的非常薄。接觸金屬層1 1 之厚度較佳爲在0.1〜7.5 nm之範圍。若薄於0」nm時， 則難於獲得穩定的薄層。超過7.5 nm時，則透光性將降低 ，因此以5 nm以下爲更佳。並且，若考慮及其後續的電流 擴散層1 2之積層所造成之透光性降低與成膜之穩定性時， 則以0.5〜2.5 nm範圍爲特佳。 ί 然而，經將接觸金屬層1 1之厚度作成爲薄時，則接觸金 屬層1 1之面方向之電阻將增大，且將與比較高電阻的ρ層 互起作用而使電流只能擴散於電流注入部的接合墊層1 3之 周邊部’以結果來看將造成不均勻的發光模式使得發光輸 出降低。 於是作爲補償接觸金屬層1 1之電流擴散性之方法而在接 觸金屬層11上配置由高光透射率且爲高導電性之金屬薄膜 所構成之電流擴散層1 2，藉此，即可在不致於對白金族金 -11 - 1257721 屬之低接觸電阻性或光透射率造成太大的負面影響下即得 以均勻地使電流擴散，其結果就是可獲得高發光輸出之發 光元件。 電流擴散層1 2之材料較佳爲選自由高導電率之金屬’例 如金、銀及銅所構成之族群之金屬或至少含有該等金屬之 一種的合金。其中金是由於作成爲薄膜時之光透射率爲高 ，因此爲最佳。 電流擴散層12之厚度較佳爲1〜20 nm。薄於1 nm時， i 則電流擴散功效不能充分發揮。超過20 nm時，則電流擴 散層1 2的光透過性之降低顯著，以致有發光輸出將降低之 顧慮，更佳爲10 nm或以下。若更進一步使厚度作成爲3〜 6 nm範圍時，則可使電流擴散層12之光透過性與電流擴 散功效之平衡趨於最佳狀態，且經使其與上述接觸金屬層 搭配，藉此，即可獲得會在正極上全面均勻地發光，且爲 高輸出的發光。 在本發明之氮化鎵系化合物半導體發光元件中，則在p § 型半導體層5之正極側表面設置含有用以形成上述接觸金 屬層之金屬的正極金屬混雜層。經採取如此之構成，即可 產生正極1 0與P型半導體層5的接觸電阻將降低之功效。 在本發明中，所謂「正極金屬混雜層」係定義爲「p型 半導體層5中含有接觸金屬層形成金屬之層」。 正極金屬混雜層之厚度較佳爲0.1〜1〇 nm。薄於〇」 及超過1 〇 n m時’則難於獲得低接觸電阻。爲獲得更佳的 接觸電阻時’則以設定爲1〜8 nm爲更佳。 -12- 1257721 另外，含在該正極金屬混雜層中的接觸金屬層形成金屬 之比率，較佳爲相對於全金屬爲〇.〇1〜原子％。少於 〇. 〇 1原子％時，則難於獲得低接觸電阻，超過3 0原子％時 ，則有將導致半導體之結晶性惡化之顧慮，較佳爲1〜2 0 原子％。此外，該正極金屬混雜層也可含有反射層形成金 屬。其時，上述比率應以將接觸金屬層形成金屬與反射層 形成金屬合算之値來加以評估。 正極金屬混雜層之厚度及所含有的正極形成金屬之比率 ，係可以該業界所熟知的剖面TEM (穿透型電子顯微鏡） 之EDS (放電）分析來加以測定。亦即，從p型半導體層 之上面（正極側面）向厚度方向實施數點，例如5點之剖 面TEM之EDS分析，然後從各點的圖表即可求得所含有 之金屬與其量。若爲決定厚度所測定之5點數據不足時， 則再追加數點來測定即可。 此外，若在正極之接觸金屬層1 1的半導體側表面設置含 有用以構成半導體的金屬之半導體金屬混雜層時，則可使 接觸電阻更加下降，因此爲較佳。亦即，在本發明中，所 謂「半導體金屬混雜層」係定義爲「接觸金屬層中含有半 導體構成金屬之層」。 半導體金屬混雜層之厚度較佳爲〇.!〜3 。薄於〇.i nm時’則接觸電阻之降低功效將不顯著。超過3 nm時， 則光透射率將減少，因此不佳，更佳爲丨〜2.5 nm。 另外，含在該半導體金屬混雜層中的半導體構成金屬之 比率較佳爲相對於全金屬量爲〇·；!〜5〇原子％。少於〇·1% -13 - 1257721 時，則降低接觸電阻之功效將不顯著。超過50原子％時， 則有導致光透射率減少之顧慮，更佳爲1〜2 0原子％。 半導體金屬混雜層之厚度及半導體構成金屬含量之測定 ，可以與正極金屬混雜層相同地以剖面TEM之EDS分析 來測定。 關於接觸金屬層1 1及電流擴散層1 2之成膜方法，並無 特殊限定，可使用習知之真空蒸鍍法或濺鍍法。 關於用來構成接合墊部之接合墊層1 3，已知有使用各種 材料的各種結構者，該等習知者可在不受到任何限制下加 以使用。但是較佳爲使用與電流擴散層之密著性良好的材 料，但是厚度則必須作成爲足夠厚以避免因在接合時之應 力而使接觸金屬層1 1或電流擴散層1 2蒙受損傷。另外， 最外表層較佳爲採用與接合球之密著性良好的材料。 本發明之透光性正極1 0，可在不受到任何限制下使用如 第1圖所示在基板1上經隔著緩衝層6而加以積層氮化鎵 系化合物半導體層2’並形成n型半導體層3、發光層4及 Ρ型半導體層5的先前習知之氮化鎵系化合物半導體發光 元件。 基板1係可在不受到任何限制下使用藍寶石單結晶（ Α12〇3 ; Α面' C面、Μ面、R面）、尖晶石單結晶（ MgAl2〇4) 、ΖηΟ單結晶、LiA102單結晶、LiGa02單結晶 、MgO單結晶等之氧化物單結晶，Si單結晶、SiC單結晶 、GaAs單結晶、A1N單結晶、GaN單結晶及ZrB2等之硼 化物單結晶寺習知基板材料。並且’基板之面方位並無特 -14- 1257721 殊限定。另外’恰當的基板也可’賦予偏移角之基板也可 〇 η型半導體層3、發光層4及p型半導體層5係已有各種 結構者爲眾所皆知，該等習知者可在不受到任何限制下加 以使用。特別是雖然ρ型半導體層5之載子濃度係使用一 般的濃度者，惟對於載子濃度爲較低者例如約1 χ 1 〇17 cnT3 之p型半導體層也可使用本發明之透光性正極。 用以構成該等之氮化鎵系化合物半導體，有一種以通式 _ AlxInyGa 卜 x-yN (0€x<l、〇Sy<l，Ogx + y<l)所代表之 各種組成的半導體是已爲眾人皆知，在本發明中用以構成 η型半導體層、發光層及P型半導體層之氮化鎵系化合物 半導體，也可在不受到任何限制下使用以通式AUIriyGan yN ( 0 S χ<1、〇 S y〈l，〇 ‘ X + y<l )所代表之各種組成之 半導體。 該等氮化錄系化合物半導體之生長方法，並無特殊限定 ，可使用金屬有機化學氣相生長法（MOCVD )、氫化氣相 • 磊晶生長法（HVPE)、分子束磊晶生長法（MBE)等之習 知可供生長III族氮化物半導體之所有方法。較佳的生長方 法，若從膜厚控制性、量產性之觀點來考慮則爲MOCVD 法。 在MOCVD法，載氣係使用氫氣（H2)或氮氣（n2), 屬III族原料之Ga源係使用二甲基錄（TMG)或三乙基鎵 (TEG ) 、A1源係使用三甲基鋁（TMA )或三乙基鋁（ TEA ) 、In源係使用三乙基銦（TMI )或三乙基銦（TEI ) -15- 1257721 、屬V族原料之氮源係使用氨氣（nh3 )、聯氨（N2H4) 等。另外’對於η型之摻質’ Si原料係使用單矽烷（SiH4 )或二矽烷（Si2H6 ) ，Ge原料係使用鍺烷（CeH4 )，對 於P型之摻質，Mg原料係使用例如雙環戊二烯基鎂（ Cp2Mg)或雙乙基環戊二烯基鎂（（EtCp)2Mg) 〇 爲接於在基板1上經將η型半導體層3、發光層4及p 型半導體層5依此順序所積層的氮化鎵系化合物半導體2 之η型半導體層3而加以形成負極2 0，則將發光層4及ρ 型半導體層5之一部份予以除去，以使η型半導體層3露 出。其後則在所留下之Ρ型半導體層’5上形成本發明之透 光性正極1 0，然後在被露出的η型半導體層3上形成負極 20。負極20已有各種組成及結構者爲眾所皆知，該等習知 之負極可在不受到任何限制下使用。 〔實施例〕 茲以實施例將本發明更詳加以說明，但是本發明並非爲 僅局限於該等者。 〔實施例〕 第2圖係在本實施例所製造之氮化鎵系化合物半導體發 光元件200之剖面模式圖，第3圖係展示其俯視模式圖。 在由藍寶石所構成之基板1上，隔著由Α1Ν所構成之緩衝 層6，將由厚度爲3 // m之非摻雜的GaN所構成之基底層 3a、厚度爲2//m之摻Si的η型GaN接觸層3b、厚度爲 0.03/zm之η型InuGao.gN包層3c、厚度爲0.03/zm之摻 Si的GaN阻障層及厚度爲2.5 nm之In〇.2Ga〇.8N井層予以 -16- 1257721 積層5層’最後則將設置阻障層的多重量子井結構之發光 層4、厚度爲0·05μπι之摻^[§的：？型AlGG7Ga().93N包層 5a、厚度爲〇.丨5 μ m之摻Mg的p型GaN接觸層5b依此順 序予以積層。 然後’在氮化鎵系化合物半導體2之p型GaN接觸層5b 上’形成由厚度爲1.5 nm之由Pt所構成之接觸金屬層1 1 、由厚度爲5 nm之由 Au所構成之電流擴散層12及由 Au/Ti/Al/Ti/Au五層結構之接合墊層13所構成之正極10。 各層之厚度係分別設定爲50、20、10、1〇〇、200 nm。 其次，在η型GaN接觸層3b上形成Ti/Au之二層結構 之負極20’以製得光取出面係位於半導體側之發光元件。 正極1 〇及負極2 0之俯視形狀如第3圖所示。 該結構之發光元件，其η型GaN接觸層3b之載子濃度 爲 lxlO19 cm·3，GaN 阻障層之 Si 摻雜量爲 lxlO18 cm·3，p 型GaN接觸層5b之載子濃度爲5xl018 cm·3，p型AlGaN 包層5a之Mg摻雜量爲5χ1019 cm·3。 氮化鎵系化合物半導體層3之積層，係以MOCVD法， 並以在該技術領域中爲眾所熟知之通常條件下實施。另外 ，正極1 〇及負極20係以下列順序形成。 起初以反應性離子蝕刻法將供形成負極之部份的η型 GaN接觸層3b以下述順序使其露出。 首先，在P型半導體層5上形成蝕刻掩模。形成順序如 下。經在全面均勻塗佈光阻劑後，使用習知微影照相術， 從比正極區域爲大一格之區域除去光阻劑。然後架設在真 -17- 1257721 空蒸鍍裝置內，在4x1 (T4 Pa以下之壓力以電子束法使Ni 及Ti積層成膜厚分別成爲約50 nm及3 00 nm。其後以剝 落法技術與光阻劑一起除去正極區域以外之金屬膜。 然後，在反應性離子蝕刻裝置之蝕刻室內電極上載置半 導體積層基板，使蝕刻室減壓成1 〇_4 P a後，蝕刻氣體供應 Cl2，施加蝕刻直至露出η型GaN接觸層3b爲止。蝕刻後 ’由反應性離子鈾刻裝置取出，以硝酸及氟酸除去上述蝕 刻掩模。 接著，使用習知微影照相術及剝落法，僅在p型GaN接 觸層5b上之供形成正極之區域，形成由Pt所構成接觸金 屬層1 1、由Au所構成電流擴散層1 2。在形成接觸金屬層 1 1、電流擴散層1 2時，則首先，將經積層氮化鎵系化合物 半導體層3之基板1放入真空蒸鍍裝置內，並在p型GaN 接觸層5b上最初將Pt予以積層1·5 nm，其次則將Au予以 積層5 nm。接著，由真空室取出後，按照通常被稱爲剝落 法之熟知順序加以處理，再以相同方法在電流擴散層1 2上 之一部份，將由Au所構成之第1層、由Ti所構成之第2 層、由A1所構成之第3層、由Ti所構成之第4層、由Au 所構成之第5層依此順序予以積層’以形成接合墊層1 3。 經以如此方式在P型GaN接觸層5b上形成本發明之正極 10 ° 經以此方法所形成之正極係具有透光性，且在470 nm之 波長區域具有60%之光透射率。該光透射率係對經以與上 述相同的接觸金屬層及電流擴散層形成爲光透射率測定用 -18 - 1257721 之大小者加以測定所得。 在第4圖擴大展示本發明之氮化鎵系化合物半導體發光 元件之P型半導體層與接觸金屬層的接合面附近。 如第4圖所示，本發明之氮化鎵系化合物半導體發光元 件，在其P型半導體層5b之接觸金屬層1 1側界面附近， 則包含含有用以形成接觸金屬層1 1之金屬的正極金屬混雜 層15b，相對地在接觸金屬層11之p型半導體層5b側界 面附近，則包含用以構成半導體層2之金屬的半導體金屬 混雜層15a。換言之，半導體金屬混雜層15a與正極金屬 混雜層15b係形成在接觸金屬層11與p型半導體層5b之 接合界面的相互擴散層1 5。由於該相互擴散層1 5之存在 ，即可發揮能獲得低電阻且具有優越的電流擴散性的接合 界面之功效。 另外，經剖面TEM之EDS分析結果，半導體金屬混雜 層15a之厚度爲1.5 nm，Ga之比率可估計爲相對於全金屬 (Pt + Au + Ga)在該層中爲1〜20原子％。正極金屬混雜 # 層15b之厚度爲6.0 nm，所設置之正極材料就是用來構成 接觸金屬層11之Pt，且其比率可估計爲相對於全金屬（Pt + Ga)在該層中爲1〜1〇原子％。第5圖係接觸金屬層的 剖面TEM之EDS分析圖表之一實例，第6圖係接觸層5b 的剖面TEM之EDS分析圖表之一實例。 如第5圖所示，在由p型GaN所構成之p型半導體層5b 之接觸金屬層1 1側界面附近之正極金屬混雜層1 5b，則有 用以形成接觸金屬層1 1之Pt存在，相對地，在接觸金屬 -19- 1257721 層1 1之P型半導體層5b側界面附近之半導體金屬混雜層 15a，則有用以構成內由GaN所構成之p型半導體層5b之 Ga存在。 另外，圖中Cu之波峰係測定所使用之X射線所造成者 〇 其次，在經露出的η型GaN接觸層3b上以下列順序形 成負極20。全面均勻地塗佈光阻劑後，使用習知微影照相 術，由被露出的η型GaN接觸層上之負極形成部份除去光 阻劑後，以通常使用之真空蒸鍍法從半導體側依照順序形 成由Ti爲100 nm、Au爲2 00 nm所構成之負極。其後以習 知方法除去光阻劑。 將經以如上述方式所形成正極1 0及負極20之基板，加 以硏削•硏磨基板背面，以使基板板厚變薄至80微米，然 後使用雷射切割機從半導體積層側經劃出割痕後予以按壓 分割成3 5 0微米方之晶片。然後，以藉由探測針的通電測 定在20 mA電流施加値之正向電壓，結果爲2.9 V。 其後，安裝於TO-18罐盒型封裝，並以測試器測量發光 輸出結果， 在施加電流20 mA時之發光輸出係顯現4 mW。而且，確 認到發光面之發光分佈係在正極上之全面發光。 〔比較例1〕 除並未設置電流擴散層以外，其餘則以與實施例相同地 製造氮化鎵系化合物半導體發光元件。結果該發光元件之 正向電壓及發光輸出係分別爲3.1 V及3.7 mW。觀察其發 -20- 1257721 光面時，正極上之發光則僅被限定在以由接合墊層周邊及 接合墊層通至負極的線上爲中心之部份。 其原因有可能是接觸金屬層之面方向電阻較高以致電流 並未擴散於接觸金屬層上之緣故。 〔比較例2〕 除並未設置電流擴散層，且使接觸金屬層之厚度改爲12 nm以外，其餘則以與實施例相同地製造氮化鎵系化合物半 導體發光元件。結果該發光元件之正向電壓及發光輸出係 @ 分別爲2·9 V及3.0 mW。觀察其發光面時，雖然與實施例 相同地可確認到在全面發光，但是接觸金屬層之光透射率 卻降低爲約3 0%，其結果發光輸出降低。 〔產業上之利用性〕 經由本發明所提供之氮化鎵系化合物半導體發光元件用 電極，係可用作爲透光型氮化鎵系化合物半導體發光元件 之正極。 【圖式簡單說明】 Φ 第1圖係展示本發明氮化鎵系化合物半導體發光元件之 剖面結構模式圖。 第2圖係展示實施例之氮化鎵系化合物半導體發光元件 之剖面結構模式圖。 第3圖係展示實施例之氮化鎵系化合物半導體發光元件 之俯視模式圖。 第4圖係展不本發明氮化鎵系化合物半導體發光元件之 p型半導體層與接觸金屬層之接合面附近擴大圖。 -21 - 1257721 第5圖係本發明氮化鎵系化合物半導體發光元件之接觸 金屬層剖面TEM的EDS分析圖表之一實例。 第6圖係本發明氮化鎵系化合物半導體發光元件之p型 半導體層剖面TEM的EDS分析圖表之一實例。 【主要元件符號說明】 1 *基板 2- 氮化鎵系化合物半導體層 3- n型半導體層 B 3a-基底層 3b-n型GaN接觸層 3c-n型InGaN包層 4- 發光層 5- p型半導體層 5a-p型AlGaN包層 5b-p型GaN接觸層 6- 緩衝層 1 0 -正極 ® 11-接觸金屬層 12-電流擴散層 1 3 -接合墊層 15-相互擴散層 15a-半導體金屬混雜層 1 5 b -正極金屬混雜層 2 0 -負極 100、2 00-氮化鎵系化合物半導體發光元件 -22-(13) The gallium nitride-based compound semiconductor light-emitting device according to any one of (1) to (1), wherein the current diffusion layer is gold. (14) The gallium nitride-based compound semiconductor light-emitting device according to any one of (1) to (1), wherein the current diffusion layer has a thickness of 1 to 2 0 nm 15(15) as the (1)~ The gallium nitride-based compound semiconductor light-emitting device according to any one of the items (14), wherein the current diffusion layer has a thickness of 1 nm or less. (16) The gallium nitride-based compound semiconductor light-emitting device according to any one of (1) to (15), wherein the current diffusion layer has a thickness of 3 to 6 (17) as in (1) to (1 6) The gallium nitride-based compound semiconductor light-emitting device according to any one of the preceding claims, wherein the bonding pad layer is made of a eutectic solder material. The gallium nitride-based compound semiconductor light-emitting device according to any one of the items (1), wherein the bonding pad layer is made of Au, Sn, or a ternary solder alloy containing Au and Sn. Composition. 1257721 The present invention is a metal having a lower contact resistance with a p-type GaN-based compound semiconductor, for example, a thin layer of a platinum group metal as a contact metal layer, and a current diffusion layer having a conductivity higher than that of the contact metal layer is provided thereon In the light-transmitting positive electrode, the diffusion of current in the direction of the positive electrode surface is improved, and as a result, the high-intensity light-emitting element having a low forward voltage (VF値) and uniformly emitting light in the positive electrode can be realized. [Embodiment] BEST MODE FOR CARRYING OUT THE INVENTION A preferred embodiment of the present invention will now be described with reference to the drawings. However, the present invention is not limited to the embodiments, and for example, the constituent elements of the embodiments may be combined as appropriate. Fig. 1 is a schematic cross-sectional view showing a gallium nitride-based compound semiconductor light-emitting device 100 having a light-transmitting positive electrode of the present invention. In the gallium nitride-based compound semiconductor light-emitting device 100 of the present invention, the gallium nitride-based compound semiconductor layer 2 is formed on the substrate 1 via the buffer layer 6, and the light-transmitting positive electrode 10 of the present invention is formed thereon. . The gallium nitride-based compound semiconductor layer 2 is composed of, for example, a heterojunction structure composed of the n-type semiconductor layer 3, the light-emitting layer 4, and the p-type semiconductor layer 5, and the negative electrode 20 is formed in one portion of the n-type semiconductor layer 3. The light-transmitting positive electrode 1 is formed in a part of the p-type semiconductor layer 5. Further, the light-transmitting positive electrode 10 is composed of three layers of the contact metal layer 1 1 , the current diffusion layer 12 and the bonding pad layer 13 . The contact resistance required for the contact metal layer 11 is such that the contact resistance with the -10-12517 of the Ρ-type semiconductor layer 5 must be small. Further, when the surface-mounted light-emitting device that extracts light from the light-emitting layer 4 from the electrode surface side is used, it is required to have excellent light transmittance. The material contacting the metal layer 11 is preferably white gold (Pt), ruthenium (RU), hungry (Os), rhodium (Rh), iridium (Ir), palladium, from the viewpoint of contact resistance with the P layer. Platinum metal or silver (Ag) of (Pd) or the like. These Pt systems are high in work function and are excellent in ohmic contact under non-heating for a relatively high-resistance P-type GaN-based compound semiconductor layer which is subjected to high-temperature heat treatment. . When the contact metal layer 1 1 is made of a platinum group metal, it is necessary to make the thickness extremely thin from the viewpoint of light transmittance. The thickness of the contact metal layer 11 is preferably in the range of 0.1 to 7.5 nm. If it is thinner than 0" nm, it is difficult to obtain a stable thin layer. When the thickness exceeds 7.5 nm, the light transmittance is lowered, so that it is preferably 5 nm or less. Further, in consideration of the decrease in light transmittance and the stability of film formation caused by the lamination of the subsequent current diffusion layer 12, it is particularly preferable in the range of 0.5 to 2.5 nm. ί However, when the thickness of the contact metal layer 11 is made thin, the resistance in the direction of the surface contacting the metal layer 11 will increase, and the ρ layer of the relatively high resistance will interact with each other to cause the current to diffuse only. The peripheral portion of the bond pad layer 13 of the current injection portion will result in an uneven light-emitting mode such that the light-emitting output is lowered. Then, as a method of compensating for the current diffusivity of the contact metal layer 11, a current diffusion layer 12 composed of a metal film having high light transmittance and high conductivity is disposed on the contact metal layer 11, thereby not being able to The current is uniformly diffused under the influence of the low contact resistance or the light transmittance of the platinum group gold-11-1257721, and as a result, a light-emitting element having a high light-emitting output can be obtained. The material of the current diffusion layer 12 is preferably a metal selected from the group consisting of high conductivity metals such as gold, silver and copper or an alloy containing at least one of the metals. Among them, gold is preferred because it has a high light transmittance when it is used as a film. The thickness of the current diffusion layer 12 is preferably from 1 to 20 nm. When thinner than 1 nm, i does not fully exert current spreading. When it exceeds 20 nm, the light transmittance of the current diffusion layer 12 is remarkably lowered, so that there is a concern that the light-emitting output is lowered, and more preferably 10 nm or less. Further, if the thickness is made to be in the range of 3 to 6 nm, the balance between the light transmittance and the current diffusion efficiency of the current diffusion layer 12 can be optimized, and it can be matched with the contact metal layer. , it is possible to obtain a light that will emit light uniformly and uniformly on the positive electrode and has a high output. In the gallium nitride-based compound semiconductor light-emitting device of the present invention, a positive electrode metal mixed layer containing a metal for forming the contact metal layer is provided on the surface of the positive electrode side of the p-type semiconductor layer 5. By adopting such a configuration, the effect of lowering the contact resistance of the positive electrode 10 and the P-type semiconductor layer 5 can be produced. In the present invention, the "positive electrode metal mixed layer" is defined as "a layer containing a metal layer forming a contact metal layer in the p-type semiconductor layer 5". The thickness of the positive electrode metal mixed layer is preferably 0.1 to 1 〇 nm. It is difficult to obtain low contact resistance when thinner than 〇" and more than 1 〇 n m. For better contact resistance, it is better to set it to 1~8 nm. Further, the ratio of the contact metal layer contained in the positive electrode metal mixed layer to form a metal is preferably 〇1〇 atom% with respect to the total metal. When it is less than 〇. 〇 1 atom%, it is difficult to obtain a low contact resistance. When it exceeds 30 atom%, there is a concern that the crystallinity of the semiconductor is deteriorated, and it is preferably 1 to 20 atom%. Further, the positive electrode metal mixed layer may also contain a reflective layer to form a metal. At this time, the above ratio should be evaluated by the combination of the metal formed by the contact metal layer and the metal formed by the reflective layer. The thickness of the positive electrode metal mixed layer and the ratio of the positive electrode forming metal contained therein can be measured by EDS (discharge) analysis of a cross-sectional TEM (transmission electron microscope) well known in the art. That is, a plurality of points (for example, a positive electrode side surface) of the p-type semiconductor layer are applied to the thickness direction, for example, EDS analysis of a TEM of a 5-point cross-section, and then the metal contained therein and the amount thereof are obtained from the graphs of the respective points. If the 5 points of data measured for determining the thickness are insufficient, a few more points may be added for measurement. Further, when a semiconductor metal mixed layer containing a metal for forming a semiconductor is provided on the semiconductor side surface of the contact metal layer 1 1 of the positive electrode, the contact resistance can be further lowered, which is preferable. That is, in the present invention, the term "semiconductor metal mixed layer" is defined as "a layer containing a metal constituting a semiconductor in a contact metal layer". The thickness of the semiconductor metal hybrid layer is preferably 〇.!~3. When thinner than 〇.i nm, the reduction in contact resistance will not be significant. When it exceeds 3 nm, the light transmittance will decrease, so it is not good, and more preferably 丨~2.5 nm. Further, the ratio of the semiconductor constituent metal contained in the semiconductor metal mixed layer is preferably 〇··~5 〇 atomic % with respect to the total metal amount. When less than 〇·1% -13 - 1257721, the effect of reducing the contact resistance will not be significant. When it exceeds 50 atom%, there is a concern that the light transmittance is lowered, and it is more preferably 1 to 20 atom%. The thickness of the semiconductor metal mixed layer and the measurement of the semiconductor constituent metal content can be measured by the EDS analysis of the cross-sectional TEM in the same manner as the positive electrode metal mixed layer. The film formation method of the contact metal layer 1 1 and the current diffusion layer 1 2 is not particularly limited, and a conventional vacuum vapor deposition method or a sputtering method can be used. Regarding the bonding pad 13 for constituting the bonding pad portion, various structures using various materials are known, and such conventional ones can be used without any restriction. However, it is preferable to use a material having good adhesion to the current diffusion layer, but the thickness must be made thick enough to avoid damage to the contact metal layer 11 or the current diffusion layer 12 due to stress at the time of bonding. Further, it is preferable that the outermost layer is made of a material having good adhesion to the bonding ball. The light-transmitting positive electrode 10 of the present invention can be laminated without any restriction to form a gallium nitride-based compound semiconductor layer 2' on the substrate 1 via the buffer layer 6 as shown in Fig. 1 and form an n-type. A conventionally known gallium nitride-based compound semiconductor light-emitting device of the semiconductor layer 3, the light-emitting layer 4, and the germanium-type semiconductor layer 5. The substrate 1 can be sapphire single crystal (Α12〇3; '面 'C surface, Μ surface, R surface), spinel single crystal (MgAl2〇4), ΖηΟ single crystal, LiA102 single crystal without any restriction. An oxide single crystal such as LiGa02 single crystal or MgO single crystal, a single crystal of Si, a single crystal of SiC, a single crystal of GaAs, a single crystal of A1N, a single crystal of GaN, and a conventional substrate material of a boride single crystal of ZrB2. And the surface orientation of the substrate is not limited to -14-1252721. Further, the 'appropriate substrate can also be used to provide a substrate having an offset angle. The 〇-type semiconductor layer 3, the light-emitting layer 4, and the p-type semiconductor layer 5 are known in various configurations, and such conventional ones can be known. Use without any restrictions. In particular, although the carrier concentration of the p-type semiconductor layer 5 is a general concentration, the light transmittance of the present invention can be used for a p-type semiconductor layer having a lower carrier concentration, for example, about 1 χ 1 〇 17 cnT3. positive electrode. In order to constitute such a gallium nitride-based compound semiconductor, there is a semiconductor having various compositions represented by the general formula _AlxInyGabx-yN (0€x<l, 〇Sy<l, Ogx + y<l) It is well known that the gallium nitride-based compound semiconductor for constituting the n-type semiconductor layer, the light-emitting layer, and the p-type semiconductor layer in the present invention can also be used without any limitation with the general formula AUIriyGan yN (0 S A semiconductor of various compositions represented by χ<1, 〇S y<l, 〇' X + y<l). The method for growing the nitride-based compound semiconductor is not particularly limited, and metal organic chemical vapor deposition (MOCVD), hydrogenation gas phase epitaxial growth (HVPE), and molecular beam epitaxy (MBE) can be used. And other methods for growing a Group III nitride semiconductor. A preferred growth method is the MOCVD method from the viewpoint of film thickness controllability and mass productivity. In the MOCVD method, the carrier gas system uses hydrogen (H2) or nitrogen (n2), and the Ga source of the Group III material uses dimethyl (TMG) or triethylgallium (TEG), and the A1 source uses trimethyl. Aluminium (TMA) or triethylaluminum (TEA), In source uses triethylindium (TMI) or triethylindium (TEI) -15-1252721, and nitrogen source of Group V raw materials uses ammonia (nh3) ), hydrazine (N2H4), etc. Further, 'for the n-type dopant' Si source, monoterpene (SiH4) or dioxane (Si2H6) is used, the Ge material is decane (CeH4), and for the P-type dopant, the Mg raw material is, for example, dicyclopentadiene. Alkenyl magnesium (Cp2Mg) or bisethylcyclopentadienyl magnesium ((EtCp) 2Mg) is bonded to the substrate 1 via the n-type semiconductor layer 3, the light-emitting layer 4, and the p-type semiconductor layer 5 in this order When the n-type semiconductor layer 3 of the gallium nitride-based compound semiconductor 2 is laminated and the negative electrode 20 is formed, one portion of the light-emitting layer 4 and the p-type semiconductor layer 5 is removed to expose the n-type semiconductor layer 3. Thereafter, the light-transmitting positive electrode 10 of the present invention is formed on the remaining germanium-type semiconductor layer '5, and then the negative electrode 20 is formed on the exposed n-type semiconductor layer 3. The negative electrode 20 is known in various compositions and configurations, and the conventional negative electrode can be used without any limitation. [Embodiment] The present invention will be described in more detail by way of examples, but the invention is not limited thereto. [Embodiment] Fig. 2 is a schematic cross-sectional view showing a gallium nitride-based compound semiconductor light-emitting device 200 manufactured in the present embodiment, and Fig. 3 is a plan view schematically showing the same. On the substrate 1 made of sapphire, a base layer 3a made of undoped GaN having a thickness of 3 // m and a Si-doped layer having a thickness of 2/m are interposed between the buffer layers 6 made of Α1Ν. The n-type GaN contact layer 3b, the n-type InuGao.gN cladding layer 3c having a thickness of 0.03/zm, the Si-doped GaN barrier layer having a thickness of 0.03/zm, and the In〇.2Ga〇.8N well having a thickness of 2.5 nm The layer is given -16- 1257721, and the fifth layer is laminated. ' Finally, the light-emitting layer 4 of the multiple quantum well structure with the barrier layer is set, and the thickness is 0·05 μπι. [§:? The Mg-doped p-type GaN contact layer 5b of the type AlGG7Ga().93N cladding layer 5a and having a thickness of 〇.丨5 μm is laminated in this order. Then, 'on the p-type GaN contact layer 5b of the gallium nitride-based compound semiconductor 2', a contact metal layer 11 composed of Pt having a thickness of 1.5 nm and a current diffusion composed of Au having a thickness of 5 nm are formed. The layer 12 and the positive electrode 10 composed of a bonding pad layer 13 of a five-layer structure of Au/Ti/Al/Ti/Au. The thickness of each layer was set to 50, 20, 10, 1 , and 200 nm, respectively. Next, a negative electrode 20' of a two-layer structure of Ti/Au is formed on the n-type GaN contact layer 3b to obtain a light-emitting element having a light extraction surface on the semiconductor side. The top view of the positive electrode 1 and the negative electrode 20 is as shown in Fig. 3. In the light-emitting element of the structure, the carrier concentration of the n-type GaN contact layer 3b is lxlO19 cm·3, the Si doping amount of the GaN barrier layer is lxlO18 cm·3, and the carrier concentration of the p-type GaN contact layer 5b is 5xl018. The cm doping amount of the cm·3, p-type AlGaN cladding layer 5a is 5χ1019 cm·3. The lamination of the gallium nitride-based compound semiconductor layer 3 is carried out by the MOCVD method under the usual conditions well known in the art. Further, the positive electrode 1 and the negative electrode 20 are formed in the following order. Initially, the n-type GaN contact layer 3b for forming a portion of the negative electrode was exposed in the following order by reactive ion etching. First, an etching mask is formed on the P-type semiconductor layer 5. The order of formation is as follows. After the photoresist is uniformly applied uniformly, the photoresist is removed from the region which is larger than the positive electrode region by conventional lithography. Then, it is installed in the true -17-1257721 air-vapor deposition device, and the film thickness of Ni and Ti layers is about 50 nm and 300 nm by electron beam method at 4x1 (pressure below T4 Pa). The metal film other than the positive electrode region is removed together with the photoresist. Then, the semiconductor laminated substrate is placed on the electrode in the etching chamber of the reactive ion etching apparatus, and the etching chamber is depressurized to 1 〇 4 P a , and the etching gas is supplied to Cl 2 . Etching is applied until the n-type GaN contact layer 3b is exposed. After etching, it is taken out by a reactive ion uranium engraving device, and the above etching mask is removed with nitric acid and hydrofluoric acid. Next, using conventional lithography and peeling, only in A region on the p-type GaN contact layer 5b for forming a positive electrode forms a contact metal layer 11 composed of Pt and a current diffusion layer 12 composed of Au. When the contact metal layer 1 1 and the current diffusion layer 12 are formed, First, the substrate 1 of the laminated gallium nitride-based compound semiconductor layer 3 is placed in a vacuum evaporation apparatus, and Pt is first laminated on the p-type GaN contact layer 5b by 1·5 nm, and then Au is laminated. 5 nm. Then, by vacuum After being taken out, it is treated in a well-known order, which is generally called a peeling method, and the first layer composed of Au and the second layer made of Ti are partially formed on the current diffusion layer 12 in the same manner. The third layer composed of A1, the fourth layer made of Ti, and the fifth layer made of Au are laminated in this order to form the bonding pad layer 13. The P-type GaN contact layer is formed in this manner. The positive electrode of the present invention is formed on 5b by 10 °. The positive electrode formed by this method has light transmissivity and has a light transmittance of 60% in a wavelength region of 470 nm. The light transmittance is the same as above. The contact metal layer and the current diffusion layer are measured and measured for the light transmittance measurement -18 - 1257721. The fourth embodiment is an enlarged view of the P-type semiconductor layer and the contact metal of the gallium nitride-based compound semiconductor light-emitting device of the present invention. In the vicinity of the bonding surface of the layer, as shown in Fig. 4, the gallium nitride-based compound semiconductor light-emitting device of the present invention contains a contact metal in the vicinity of the interface of the P-type semiconductor layer 5b on the side of the contact metal layer 1 1 side. Layer 1 1 metal The electrode metal hybrid layer 15b is opposite to the interface of the p-type semiconductor layer 5b on the side of the contact metal layer 11, and includes a semiconductor metal hybrid layer 15a for constituting the metal of the semiconductor layer 2. In other words, the semiconductor metal mixed layer 15a and the positive electrode metal The hybrid layer 15b is formed in the interdiffusion layer 15 of the bonding interface between the contact metal layer 11 and the p-type semiconductor layer 5b. Due to the existence of the interdiffusion layer 15, it is possible to obtain low resistance and superior current diffusivity. In addition, the thickness of the semiconductor metal hybrid layer 15a is 1.5 nm, and the ratio of Ga can be estimated to be 1 in the layer relative to the total metal (Pt + Au + Ga). ~20 atomic %. The positive electrode metal hybrid # layer 15b has a thickness of 6.0 nm, and the positive electrode material is used to form the Pt of the contact metal layer 11, and the ratio thereof can be estimated to be 1 to 1 in the layer with respect to the total metal (Pt + Ga). 1 〇 atomic %. Fig. 5 is an example of an EDS analysis chart of a cross-sectional TEM of a contact metal layer, and Fig. 6 is an example of an EDS analysis chart of a cross-sectional TEM of the contact layer 5b. As shown in FIG. 5, in the positive electrode metal mixed layer 15b in the vicinity of the interface of the p-type semiconductor layer 5b made of p-type GaN, which is in contact with the metal layer 1 1 side, it is useful to form the Pt of the contact metal layer 1 1 . On the other hand, in the semiconductor metal-hybrid layer 15a in the vicinity of the side of the P-type semiconductor layer 5b on the side of the metal layer 195-15271, the Ga is formed to constitute the p-type semiconductor layer 5b made of GaN. Further, the X-rays used for the measurement of the crest system of Cu in the figure 〇 Next, the negative electrode 20 is formed in the following order on the exposed n-type GaN contact layer 3b. After the photoresist is completely and uniformly coated, the photoresist is removed from the negative electrode forming portion on the exposed n-type GaN contact layer by conventional lithography, and then vacuum-deposited from the semiconductor side by a commonly used vacuum evaporation method. A negative electrode composed of Ti of 100 nm and Au of 200 nm was formed in this order. The photoresist is then removed by conventional methods. The substrate of the positive electrode 10 and the negative electrode 20 formed as described above is honed and honed to the back surface of the substrate to thin the substrate thickness to 80 μm, and then drawn out from the side of the semiconductor laminate using a laser cutter. After the cut, it is pressed and divided into wafers of 305 micrometers. Then, the forward voltage applied to the current of 20 mA was measured by the energization of the probe pin, and the result was 2.9 V. Thereafter, it was mounted in a TO-18 can-type package, and the illuminating output was measured with a tester, and the illuminating output appeared to be 4 mW at a current of 20 mA. Further, it was confirmed that the light emission distribution of the light-emitting surface was comprehensively illuminated on the positive electrode. [Comparative Example 1] A gallium nitride-based compound semiconductor light-emitting device was produced in the same manner as in the Example except that the current diffusion layer was not provided. As a result, the forward voltage and the light-emitting output of the light-emitting element were 3.1 V and 3.7 mW, respectively. When the -20-1252721 smooth surface is observed, the light emission on the positive electrode is limited only to the portion centered on the line passing through the periphery of the bonding pad and the bonding pad to the negative electrode. The reason may be that the direction resistance of the surface of the contact metal layer is high so that the current does not diffuse on the contact metal layer. [Comparative Example 2] A gallium nitride-based compound semiconductor light-emitting device was produced in the same manner as in the Example except that the current diffusion layer was not provided and the thickness of the contact metal layer was changed to 12 nm. As a result, the forward voltage and the light-emitting output of the light-emitting element were respectively 2. 9 V and 3.0 mW. When the light-emitting surface was observed, it was confirmed that the light-emitting transmittance of the contact metal layer was reduced to about 30% as in the case of the entire example, and as a result, the light-emitting output was lowered. [Industrial Applicability] The electrode for a gallium nitride-based compound semiconductor light-emitting device provided by the present invention can be used as a positive electrode of a light-transmitting gallium nitride-based compound semiconductor light-emitting device. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic cross-sectional structural view showing a gallium nitride-based compound semiconductor light-emitting device of the present invention. Fig. 2 is a schematic cross-sectional structural view showing a gallium nitride-based compound semiconductor light-emitting device of the embodiment. Fig. 3 is a plan view showing a plan view of a gallium nitride-based compound semiconductor light-emitting device of the embodiment. Fig. 4 is an enlarged view showing the vicinity of the joint surface of the p-type semiconductor layer and the contact metal layer of the gallium nitride-based compound semiconductor light-emitting device of the present invention. -21 - 1257721 Fig. 5 is an example of an EDS analysis chart of the contact metal layer cross-section TEM of the gallium nitride-based compound semiconductor light-emitting device of the present invention. Fig. 6 is a view showing an example of an EDS analysis chart of a cross-sectional TEM of a p-type semiconductor layer of a gallium nitride-based compound semiconductor light-emitting device of the present invention. [Description of main component symbols] 1 *Substrate 2 - Gallium nitride compound semiconductor layer 3 - n type semiconductor layer B 3a - Base layer 3b - n type GaN contact layer 3c - n type InGaN cladding layer 4 - Light emitting layer 5 - p Type semiconductor layer 5a-p type AlGaN cladding layer 5b-p type GaN contact layer 6 - buffer layer 10 - positive electrode 11 - contact metal layer 12 - current diffusion layer 1 3 - bonding pad layer 15 - interdiffusion layer 15a - semiconductor Metal mixed layer 1 5 b - positive metal mixed layer 2 0 - negative electrode 100, 200-gallium nitride compound semiconductor light-emitting element-22-