1311818 九、發明說明： 【發明所屬之技術領域】 本發明係有關透明電極（正電極），並特指具有極佳穿 透性與歐姆性質且適用於在紫外光區發光之氮化鎵系化合 物半導體發光裝置的透明電極。 【先前技術】 近年來，氮化鎵系化合物半導體材料已在作爲短波發 光裝置用之半導體材料上受到注目。氮化鎵系化合物半導 體的形成係使用各種以藍寶石單晶爲初始材料的氧化物基 板或各種III-V族化合物基板，並藉由金屬有機化學氣相沈 積法（MOCVD法）及分子束磊晶法（MBE法）等而將相關化合 物堆疊於其上。 氮化鎵系化合物半導體材料的特徵爲橫向電流擴散很 小。雖然尙未徹底瞭解該小電流的原因，惟依邏輯推斷其 可歸咎於發生在磊晶內及由基板穿透其表面的諸多差排。 此外，相較於η型氮化鎵系化合物半導體，p型氮化鎵系 化合物半導體（以下有時簡稱爲"ρ層”）具有較高電阻率。當 僅具有一金屬堆疊於Ρ型半導體層表面時，其實質無橫向 擴散電流。當LED結構設有ρ-η接面時，其僅在正電極正 下方發光。 在該狀況下’目前正風行藉由電子束輻射作用或高溫 退火降低Ρ層電阻率而提高ρ層中的電流擴散性。然而， 電子束輻射需要一極昂貴的裝置而無助於生產成本。此外 ’其在整個晶圓內部進行均勻處理時亦招致困難。爲使其 1311818 效果顯著，高溫退火處理具有需在超過90(TC之溫度進行 的製程。在該製程期間，GaN的晶體結構開始分解，且氮 分解可能造成逆向電壓特性的劣化。 已有人提出藉由各沈積數十nm適當厚度的鎳與金於p 層上，並將所形成的複合正電極進行合金處理（參考諸如曰 本專利2803 742)，以降低p層電阻率，並形成具有穿透性 與歐姆性的正電極。 然而，在使用金作爲透明電極的狀況中，使用其於紫 外線發射裝置時會有發光輸出大幅降低的問題。雖然金爲 在藍光區中具有極佳穿透率的金屬，惟其透明度不佳，因 爲其在44 Onm以下之紫外線區的穿透率約爲藍光區的90% 〇 其次，在氧氣氛下的合金處理會有氧化層形成在暴露 η型GaN層之表面上的問題，因而影響負電極的歐姆性質 、使電極形成網狀結構且易於發生不均勻發光。 更有人提出藉由形成鉑正電極於P層上並在含氧氣氛 中熱處理所形成的物質而使P層可同時降低電阻率並進行 合金處理（參考諸如JP-A HEI 1 1 - 1 86605)。然而，該方法亦 具有前揭問題，因爲其需要在氧氣氛中進行熱處理。爲以 簡單的鉑物質形成極佳的透明電極，該電極厚度必須降低 至一相當程度（5 nm或更薄）。該要求將使鉑層電阻率變高 ，縱使在藉由熱處理而使鉑層電阻率降低時亦會削弱電流 擴散，損及發光均勻性，以及造成正向電壓（VF)上升發光 強度下降。 1311818 爲解決前揭問題，本發明之目的在於提供—種1 電極），其在紫外光區具有極佳穿透性、並具有低接 率及極佳電流擴散性，且無須進行電子束照射、高 或氧氣氛中的合金熱處理。 【發明內容】 爲達成前揭目的，本發明的第一個觀點提供一 極於440nm或更短發光波長的氮化鎵系化合物半導 裝置，該透明電極包含一金屬層鄰接配置於P型半 與一電流擴散層配置於金屬層上，該透明電極在其 域實質上不含金，該金屬層含有選自由Pt, Ir, Ru | 組成之族群中的任一元素作爲主成分，以及該電流 含有選自由Pt, Ir，Ru與Rh所組成之族群中的任一 爲主成分，惟該金屬層與電流擴散層不得具有相同 〇 在包含第一個觀點的本發明第二個觀點中，透 具有300nm至440nm範圍的發光波長。 在包含第一或第二個觀點的本發明第三個觀點 明電極在鄰接P型半導體層的區域中含有Pt作爲主 在包含第一至第三個觀點中之任一項的本發明 觀點中，金屬層具有Pt作爲主成分，且電流擴散層 自由Pt，Ir, Ru與Rh所組成之族群中的任一元素作 分。 在包含第一至第四個觀點中之任一項的本發明 觀點中，金屬層具有0.1至20nm範圍的薄膜厚度。 I極（正 觸電阻 溫退火 透明電 體發光 導體層 整個區 } Rh所 擴散層 元素作 組成物 明電極 中，透 成分。 第四個 具有選 爲主成 第五個 1311818 在包含第一至第五個觀點中之任一項的本發明第六個 觀點中，電流擴散層具有I至2 Οηηι範圍的薄膜厚度。 在包含第一至第六個觀點中之任一項的本發明第七個 觀點中，形成於其上的金屬層與電流擴散層並未進行熱處 理。 在包含第一至第七個觀點中之任一項的本發明第八個 觀點中，穿透透明電極的光爲入射光的60%或更高。 本發明的第九個觀點亦提供設有如第一至第八個觀點 之任一項的透明電極的白光發光裝置。 本發明的第十個觀點亦提供使用如第九個觀點之白光 發光裝置的白光發光燈具。 本發明的第十一個觀點亦提供使用如第十個觀點之白 光發光燈具的照明裝置。 該透明電極實質上未含金，縱使在紫外光區亦具有極 佳穿透性，具有諸如鈾的金屬薄層，以及因一金屬層（接觸 金屬層）接觸於P型GaN系化合物半導體層而對該p型GaN 系化合物半導體層具有低電阻率，所以該透明電極將裝置 發射的光線穿透至外部的性質極佳。在此使用的術語"實質 上無金”意指金含量爲1%或更低，且〇.1 %或更低爲較佳。 其次’設有導電率高於（電阻率低於）接觸金屬層之電流擴 散層的本發明透明正電極得以提高平面方向的電流擴散， 因而得以製造具有低正向電壓（VF値）且整個正電極表面發 光均勻的高照度發光裝置。 本發明的前揭及其他目的、特徵與優點將參考附圖並 1311818 由下列說明而爲熟諳本技藝者所瞭解。 【實施方式】 本發明的透明正電極係由任何區域皆不含金的金屬所 形成，並將參考附圖做說明。 第1圖爲設有本發明透明正電極之發光裝置的橫剖面 示意圖’其中參考數字11代表接觸金屬層，數字12爲電 流擴散層’且數字13爲接合墊層。參考數字11與12共同 組成本發明的透明正電極1 〇。此外，參考數字I代表基板 ’數字2爲在紫外光區發光並由n型半導體層3、發光層4 及Ρ型GaN系化合物半導體層5所形成的GaN系化合物半 導體層，數字6代表緩衝層，以及數字20爲負電極。 含有接觸金屬層與電流擴散層之透明電極的任何區域 皆不含金便可使其在紫外光區具有令人滿意的透光性。 必要的接觸金屬層性質包含與ρ型GaN系化合物半導 體層的低接觸電阻率。此外，用於穿經電極平面端而由發 光層發出紫外光區之光線的面朝上安裝型發光裝置希冀具 有極佳穿透性。 由與ρ型GaN系化合物半導體層之接觸電阻率與紫外 光穿透率的觀點，接觸金屬層材料包含選自由鉑（Pt)、釕（RU) 、铑（Rh)與銥（Ir)所組成之族群中的至少一種元素作爲主成 分。在前揭元素中，Pt爲特佳，因爲其具有高功函數而得 以獲得無須在高溫熱處理的P型GaN系化合物半導體層， 並具有相當高的電阻率而無須加熱便可獲得極佳歐姆電阻 率。 1311818 當接觸金屬層由諸如Pt形成時，由透光性的觀點，該 薄層厚度必須相當小。接觸金屬層厚度最好爲0.1至20 nm 。倘若厚度低於0 _ 1 n m，則將無法輕易且穩定地獲得該薄 層。倘若厚度超過20nm，其將造成透光度降低。該範圍上 限爲1 Onm或更小爲更佳。考量因後續電流擴散層堆疊所造 成的穿透性劣化及薄膜形成的穩定性，0.5至6nm範圍爲 特佳。 然而，減小接觸金屬層厚度將使接觸金屬層平面方向 上的電阻率升高’而與p型半導體層的高電阻率耦合之該 升高的電阻率會使電流無法在襯墊層周邊部位（電流注入 部位）以外的任一部位中擴散。所以，發光圖案並不均勻且 發光輸出劣化。 因此，藉由在接觸金屬層上配置由高透光性且高導電 性金屬薄膜所形成的電流擴散層，以作爲補償接觸金屬層 之電流擴散性質的方式，便得以均勻擴散電流，而不會嚴 重損及金屬薄膜的低接觸電阻率及透光性。 電流擴散層的材料包含選自由鉑（Pt)、釕（Ru)、铑（Rh) 與銥（1〇所組成之族群中的至少一種元素作爲主成分。此外 ，可摻入金以外的高導電率金屬（亦即，銀、銅及其合金） 至不會損及穿透性的程度。雖然前揭元素同接觸金屬層， 惟結合使用的電流擴散層及接觸金屬層係選用不同的元素 。該元素的最佳組合爲接觸金屬層使用Pt，並由Pt, Ir, Ru 與Rh組成的族群中選用任一元素作爲電流擴散層的主成 分。 -10- 1311818 - 電流擴散層的厚度最好爲1至2 0 n m的範圍。倘若厚度 不足1 nm ’則該不足將使電流擴散效果不完全。倘若超過 2 Onm ’其將明顯劣化電流擴散層的透光性並劣化發光輸出 。1 Onm或更小爲更佳。進一步將厚度範圍限制在3至6nm 便得以最佳化電流擴散層透光性與電流擴散效果間的平衡 ，而得以在正電極結合接觸金屬層時使整個正電極表面產 生均勻發光並獲得高輸出。本發明所使用的術語"穿透性’， 意指在440nm或更小波長區的透光性（特指在30〇至4〇〇nrn ® 的範圍），惟其無須完全透明。穿透性最好得以通過6 Ο %或 更高的光線。 形成接觸金屬層與電流擴散層的方法並未特別限定， 惟其可選自諸如真空沈積及濺鍍等熟知的方法。 組成接合墊部位的接合墊層已用於使用各種材料的各 種結構中。可採用該熟知的接合塾層，而無任何特殊限制 。諸如可採用Au/Ti/Al/Ti/Αυ五層結構。接合墊層最好使 用對電流擴散層的黏著性極佳的材料，並具有足以避免接 I 合期間產生的應力損傷接觸金屬層或電流擴散層的厚度。 • 最外表面層最好由諸如Au的金屬形成，其對於接合球具有 極佳黏著性。 本發明所希虞的透明正電極可不受限地使用於習用熟 知的氮化鎵化合物半導體發光裝置，如第1圖所示，該氮 化鎵化合物半導體發光裝置的形成係經由緩衝層而將一個 氮化鎵系化合物半導體堆疊於基板上，並於其上形成一 n 型半導體層、一發光層及一 p型半導體層。 -11- 1311818 - 就基板而言，可使用任一熟知的基板材料而無任何限 制，諸如包含藍寶石單晶（Al2〇3 :A平面、C平面、M平面 與R平面）、尖晶石單晶（MgAl204)、ΖηΟ單晶、LiA102單 晶、LiGa02單晶與MgO單晶的氧化物單晶、矽單晶、SiC 單晶、GaAs單晶、A1N單晶、GaN單晶及包含ZrB2的硼 單晶。順帶一提，基板的平面取向並未特別限制。該基板 可爲單純的基板或去角的基板。 η型半導體層、發光層及p型半導體層係廣用於各種 • 結構，且可使用這些廣用的薄層。雖然Ρ型半導體層特別 使用一般的載體濃度，但是本發明的透明正電極甚至可應 用於具有諸如約1 X 1 〇17cnT3之相當低載體濃度的ρ型半導 體層。 氮化鎵系化合物半導體係廣用於以通式AlxInyGai.x_yN (OS x< 1，OS y< 1，OS x + y < 1)所示的各種組成物。對於 形成η型半導體層與ρ型半導體層的氮化鎵系化合物半導 體而言，這些以通式 AlxInyGai.x.yN(0Sx< 1，0gy< 1，0 ® $ x + y< 1)表示之廣用的各種組成物的半導體皆可使用，而 . 無任何限制。 爲在紫外光區中發光，主動層係使用銦濃度約1 0%或 更低的組成物。該濃度可以井層膜厚、阻障層組成物及主 動層載體濃度進行控制。 成長氮化鎵系化合物半導體的方法並未特別限制。可 採用用於成長ΠΙ族氮化物半導體的熟知方法，諸如MOCVD (金屬有機化學氣相沈積）法、HVPE(氫化物蒸氣相磊晶）法 -12- 1311818 及MBE(分子束磊晶）法。由控制膜厚性質與量產的觀點， 較佳的成長方法爲MOCVD法。MOCVD法係使用氫氣（H2) 或氮氣（N〇作爲載體氣體’三甲烷基鎵（TmG)或三乙烷基鎵 (TEG)作爲m族原料的鎵源，三甲烷基鋁（TMA)或三乙烷基 鋁（TEA)作爲鋁源，三甲烷基銦（TMI)或三乙烷基銦（TEI)作 爲銦源’以及氨（NH3)或聯胺（N2H4)作爲V族原料的氮源。 作爲矽原料的單矽烷（SiH4)或雙矽烷（Si 2H6)及作爲鍺原料 的鍺烷（GeH4)爲p型的摻質，而諸如作爲鎂原料的雙環戊 I 二烯基鎂（CpzMg)或雙乙基雙環戊二烯基鎂（（EtCp)2Mg)係 作爲P型的摻質。 爲形成接觸於氮化鎵系化合物半導體之η型半導體層 的負電極（其中該氮化鎵系化合物半導體係藉由依序堆疊η 型半導體層、發光層及Ρ型半導體層於基板上而形成），發 光層及Ρ型半導體層係部分移除而暴露出η型半導體層。 其次，本發明的透明正電極形成於ρ型半導體層的其餘部 位，且負電極形成於暴露的η型半導體層。該負電極係廣 > 用於各種組成物及各種結構。可在無任何限制下使用該廣 用的負電極。 本發明現將參考實例而更具體地說明如下。本發明並 非僅限於該實例。 實例1 : 第2圖爲以本實例所製造之氮化鎵系化合物半導體紫 外光發光裝置的橫剖面示意圖，而第3圖爲其平面示意圖 。在藍寶石形成的基板1上經由Α1Ν緩衝層6而堆疊有8 -13- •1311818 微米厚度的GaN未摻雜底層3a、2微米厚的摻矽^型A1GaN 接觸層3b' 0.03微米的η型inG1GaQ 9N覆層3c，16nm厚 的摻砂Al〇.iGac.9N阻障層及4nm厚的Inu2Ga() 98n井層係 以五個循環父錯堆疊於其上，以及最後設有阻障層之多量 子井結構的發光層4、〇.01微米厚的摻鎂p型A1() Q7GaQ 93n 覆層5a及0.15微米厚的摻鎂p型AiGaN接觸層5b係依序 堆疊於其上。氮化鎵系化合物半導體的p型AlGaN接觸層 上堆疊有1.5nm厚的鉑接觸金屬層η及3nm厚的铑電流擴 散層1 2，以形成本發明的正電極丨〇。在電流擴散層上形成 有 Au/Ti/Al/Ti/Au 五層結構（厚度各爲 5〇/2〇/1〇/1〇〇/2〇〇 nm)的接合墊層13。其次，Ti/Au雙層結構的負電極20係 形成於η型AiGaN接觸層上，以形成具有發光平面於半導 體端的發光裝置。正電極與負電極的形狀如第3圖所示。 在該結構中’η型AiGaN接觸層的載體濃度爲ix1()'9cm-3 ，該AiGaN阻障層中的矽摻質量爲lxi〇i8cm-3, p型AiGaN 接觸層的載體濃度爲5xl018cm_3，p型AiGaN阻障層中的 鎂摻質量爲5xl019cnT3。 氮化鎵系化合物半導體層的堆疊係於相關技術領域所 熟知的條件下以MOCVD進行之。正電極與負電極係以下 列步驟形成。 首先，藉由活性離子蝕刻技術而形成負電極於其上之 η型AiGaN接觸層的一部分係以下列步驟進行暴露。 起先，將蝕刻遮罩形成於P型半導體層上。該形成方 式如下。將光阻劑均勻施加於整個表面，並藉由熟知的微 -14- 1311818 - 影技術在所施加的光阻劑塗佈物上移除尺寸較正電極區爲 大的區域。將經遮罩的p型半導體層置於真空沈積裝置中 ，並在4x1 0_4pa或更低的壓力下藉由電子束技術而個別沈 積5 Onm與3 0 0nm膜厚的鎳與鈦於其上。其次，以剝除技 術將金屬膜與正電極區外的光阻劑剝除。 其次，將半導體堆疊基板安裝於活性離子蝕刻裝置之 蝕刻艙內的電極上，蝕刻艙壓縮至1 (Γ4 P a，氯氣供應至該 艙內以作爲蝕刻氣體，以及繼續蝕刻以暴露出η型AlGaN # 接觸層。在蝕刻後，由活性離子蝕刻裝置取出半導體堆疊 基板，並以硝酸與氫氟酸移除蝕刻遮罩。 其次，藉由熟知的微影技術與剝除技術而將鉑接觸金 屬層與鍺電流擴散層單獨形成在用於將正電極形成於P型 AlGaN接觸層上的區域內。在形成接觸金屬層與電流擴散 層時，首先將具有氮化鎵系化合物半導體層堆疊於其上的 基板置於真空沈積艙內，先於p型AlGaN接觸層上沈積 1.5nm厚度的鉑，再沈積3nm厚度的鍺。因此，本發明的 Φ 正電極係形成於P型AlGaN接觸層上。其次，由真空艙取 _ 出所形成的基板，並根據廣知的步驟（通常稱爲"剝除"）進行 處理。此外，以類似步驟依序堆疊金形成的第一層、鈦形 成的第二層、鋁形成的第三層、鈦形成的第四層及金形成 的第五層，而形成接合墊層於部分的電流擴散層上。 本發明可避免透明電極部位含有金，且未觀察到金夾 雜於接合墊中。金爲接合性極佳的金屬。接合墊最上層之 金的形成係以諸如普通的方式形成。 -15- 1311818 以本方法所形成的正電極具有穿透性，並於405nm的 波長區內具有70%的透光率。該透光率係使用藉由形成前 揭相同接觸金屬層與電流擴散層而獲得的試樣而進行判斷 ，其中該試樣具有用於判斷透光率的預定尺寸。1311818 IX. DESCRIPTION OF THE INVENTION: TECHNICAL FIELD The present invention relates to a transparent electrode (positive electrode), and particularly to a gallium nitride compound having excellent penetrability and ohmic properties and suitable for emitting light in an ultraviolet region. A transparent electrode of a semiconductor light emitting device. [Prior Art] In recent years, gallium nitride-based compound semiconductor materials have been attracting attention as semiconductor materials for short-wavelength light-emitting devices. The gallium nitride-based compound semiconductor is formed by using various oxide substrates or various III-V compound substrates using sapphire single crystal as a starting material, and by metal organic chemical vapor deposition (MOCVD) and molecular beam epitaxy. A related compound is stacked thereon by a method (MBE method) or the like. The gallium nitride based compound semiconductor material is characterized by a small lateral current diffusion. Although the reason for this small current is not fully understood, it is logically inferred that it can be attributed to many misalignments occurring in the epitaxial crystal and penetrating the surface by the substrate. Further, the p-type gallium nitride-based compound semiconductor (hereinafter sometimes abbreviated as "p layer") has a higher resistivity than the n-type gallium nitride-based compound semiconductor. When there is only one metal stacked on the germanium type semiconductor When the surface of the layer is substantially free of lateral diffusion current. When the LED structure is provided with a ρ-η junction, it emits light only under the positive electrode. Under this condition, 'currently popular is reduced by electron beam irradiation or high temperature annealing. The layer resistivity increases the current diffusivity in the p layer. However, electron beam irradiation requires a very expensive device and does not contribute to the production cost. Moreover, it also causes difficulty in uniform processing throughout the wafer. Its 1311818 effect is remarkable, and the high temperature annealing treatment has a process that needs to be performed at a temperature exceeding 90 (TC). During this process, the crystal structure of GaN starts to decompose, and nitrogen decomposition may cause deterioration of reverse voltage characteristics. It has been proposed by each Depositing tens of nm of appropriate thickness of nickel and gold on the p layer, and alloying the formed composite positive electrode (refer to, for example, 曰本 patent 2803 742) to reduce p Resistivity, and forming a positive electrode having permeability and ohmicity. However, in the case where gold is used as the transparent electrode, there is a problem that the light-emitting output is greatly lowered when it is used in the ultraviolet light-emitting device. Although gold is in the blue light region. A metal with excellent penetration, but its transparency is poor, because its transmittance in the ultraviolet region below 44 Onm is about 90% of that in the blue region. Second, the alloy treatment in an oxygen atmosphere has an oxide layer. The problem of exposing the surface of the n-type GaN layer, thus affecting the ohmic properties of the negative electrode, causing the electrode to form a network structure and prone to uneven luminescence. It has been proposed to form a platinum positive electrode on the P layer and in oxygen. The material formed by heat treatment in the atmosphere allows the P layer to simultaneously reduce the resistivity and perform alloy treatment (refer to, for example, JP-A HEI 1 1 - 1 86605). However, this method also has a problem as it requires an oxygen atmosphere. Heat treatment is carried out. To form an excellent transparent electrode with a simple platinum material, the electrode thickness must be reduced to a considerable extent (5 nm or less). This requirement will result in a platinum layer. The resistivity becomes higher, even when the resistivity of the platinum layer is lowered by heat treatment, the current diffusion is impaired, the uniformity of the light is impaired, and the forward voltage (VF) is increased. The luminous intensity is lowered. 1311818 To solve the above problem, The object of the present invention is to provide an alloy (1 electrode) which has excellent penetration in an ultraviolet region, has a low connection rate and excellent current diffusivity, and does not require electron beam irradiation, an alloy in a high or oxygen atmosphere. SUMMARY OF THE INVENTION In order to achieve the foregoing object, a first aspect of the present invention provides a gallium nitride-based compound semiconductor device having a light-emitting wavelength of 440 nm or shorter, wherein the transparent electrode includes a metal layer adjacent to the P. a type of semi-and a current diffusion layer disposed on the metal layer, the transparent electrode being substantially free of gold in its domain, the metal layer containing any element selected from the group consisting of Pt, Ir, Ru | as a main component, and The current contains any one of the group consisting of Pt, Ir, Ru and Rh as the main component, but the metal layer and the current diffusion layer must not have the same 〇 in the present aspect containing the first viewpoint Second aspect, the lens having a light emission wavelength range of 300nm to 440nm. In a third aspect of the present invention comprising the first or second aspect, the electrode contains Pt in a region adjacent to the P-type semiconductor layer as a main point in the inventive concept including any one of the first to third aspects The metal layer has Pt as a main component, and the current diffusion layer is free of any one of the groups consisting of Pt, Ir, Ru and Rh. In the aspect of the invention comprising any one of the first to fourth aspects, the metal layer has a film thickness in the range of 0.1 to 20 nm. I-pole (positive-contact resistance temperature-annealing transparent electric-light-emitting conductor layer entire region} Rh-diffused layer element is used as a composition in the bright electrode, and the component is transmissive. The fourth has the main selection as the fifth 1311818 in the first to the first In a sixth aspect of the invention according to any one of the five aspects, the current diffusion layer has a film thickness in the range of 1 to 2 Οηηι. The seventh invention of the present invention comprising any one of the first to sixth aspects In view of the above, the metal layer and the current diffusion layer formed thereon are not subjected to heat treatment. In the eighth aspect of the invention comprising any one of the first to seventh aspects, the light penetrating the transparent electrode is incident 60% or more of light. The ninth aspect of the present invention also provides a white light emitting device provided with a transparent electrode according to any one of the first to eighth aspects. The tenth aspect of the present invention also provides the use of A white light emitting lamp for a white light emitting device of nine points. An eleventh aspect of the present invention also provides an illumination device using the white light emitting lamp of the tenth aspect. The transparent electrode is substantially free of gold, even in purple The external light region also has excellent penetrability, has a thin metal layer such as uranium, and has a low contact to the p-type GaN-based compound semiconductor layer due to contact of a metal layer (contact metal layer) with the P-type GaN-based compound semiconductor layer. Resistivity, so the transparent electrode has excellent properties of penetrating the light emitted from the device to the outside. The term "substantially no gold" as used herein means that the gold content is 1% or less, and 〇.1% or Lower is preferred. Secondly, the transparent positive electrode of the present invention having a current diffusion layer having a conductivity higher than (resistivity lower than) the contact metal layer can increase the current diffusion in the planar direction, thereby producing a low forward voltage ( The present invention is also to be understood by those skilled in the art from the following description. The transparent positive electrode of the present invention is formed of a metal containing no gold in any region, and will be described with reference to the accompanying drawings. Fig. 1 is a cross section of a light-emitting device provided with a transparent positive electrode of the present invention. Schematic 'where reference numeral 11 represents a contact metal layer, numeral 12 is a current diffusion layer' and numeral 13 is a bond pad layer. Reference numerals 11 and 12 together constitute a transparent positive electrode 1 本 of the present invention. Further, reference numeral I represents a substrate ' The numeral 2 is a GaN-based compound semiconductor layer which emits light in the ultraviolet region and is formed of the n-type semiconductor layer 3, the light-emitting layer 4, and the germanium-type GaN-based compound semiconductor layer 5, numeral 6 represents a buffer layer, and numeral 20 is a negative electrode. Any region containing a transparent electrode contacting the metal layer and the current diffusion layer does not contain gold, so that it has satisfactory light transmittance in the ultraviolet region. The necessary contact metal layer properties include the p-type GaN-based compound semiconductor layer. In addition, the face-up mounting type light-emitting device for passing through the flat end of the electrode and emitting light of the ultraviolet region by the light-emitting layer has excellent penetration. The contact metal layer material is selected from the group consisting of platinum (Pt), ruthenium (RU), rhodium (Rh) and iridium (Ir) from the viewpoint of contact resistivity and ultraviolet light transmittance with the p-type GaN-based compound semiconductor layer. At least one element of the group is used as a main component. Among the former elements, Pt is particularly excellent because it has a high work function to obtain a P-type GaN-based compound semiconductor layer which does not require high-temperature heat treatment, and has a relatively high electrical resistivity without obtaining an excellent ohmic resistance. rate. 1311818 When the contact metal layer is formed of, for example, Pt, the thickness of the thin layer must be relatively small from the viewpoint of light transmittance. The thickness of the contact metal layer is preferably from 0.1 to 20 nm. If the thickness is less than 0 _ 1 n m, the thin layer will not be easily and stably obtained. If the thickness exceeds 20 nm, it will cause a decrease in light transmittance. The upper limit of this range is preferably 1 Onm or less. Considering the deterioration of the penetration and the stability of film formation caused by the subsequent stacking of the current diffusion layers, the range of 0.5 to 6 nm is particularly preferable. However, reducing the thickness of the contact metal layer will increase the resistivity in the planar direction of the contact metal layer' and the increased resistivity coupled with the high resistivity of the p-type semiconductor layer will prevent current from flowing around the periphery of the liner layer. Diffusion in any part other than (current injection site). Therefore, the illuminating pattern is not uniform and the illuminating output is deteriorated. Therefore, by disposing a current diffusion layer formed of a highly transparent and highly conductive metal thin film on the contact metal layer, as a method of compensating for the current diffusion property of the contact metal layer, the current can be uniformly diffused without Severe damage to the low contact resistivity and light transmission of the metal film. The material of the current diffusion layer contains at least one element selected from the group consisting of platinum (Pt), ruthenium (Ru), rhodium (Rh), and ruthenium (1 作为) as a main component. Further, high conductivity other than gold may be incorporated. The rate of metal (ie, silver, copper, and alloys thereof) does not impair the degree of penetration. Although the elements disclosed above are in contact with the metal layer, the current diffusion layer and the contact metal layer used in combination are different elements. The best combination of this element is Pt using a contact metal layer, and any one of Pt, Ir, Ru and Rh is selected as the main component of the current diffusion layer. -10- 1311818 - The thickness of the current diffusion layer is the best It is in the range of 1 to 20 nm. If the thickness is less than 1 nm', the deficiency will make the current diffusion effect incomplete. If it exceeds 2 Onm', it will significantly degrade the light transmittance of the current diffusion layer and degrade the light output. 1 Onm or Smaller is better. Further limiting the thickness range to 3 to 6 nm optimizes the balance between the current diffusion layer transmittance and the current diffusion effect, and enables the entire positive electrode surface to be produced when the positive electrode is combined with the contact metal layer. All Luminescence and high output. The term "penetration' as used in the present invention means translucency in the wavelength region of 440 nm or less (specifically in the range of 30 〇 to 4 〇〇 nrn ® ), but it is not necessary It is completely transparent. The penetration is preferably passed through 6 Ο % or higher. The method of forming the contact metal layer and the current diffusion layer is not particularly limited, but may be selected from well-known methods such as vacuum deposition and sputtering. The bonding pad layer of the bonding pad portion has been used in various structures using various materials. The well-known bonding bonding layer can be employed without any particular limitation. For example, an Au/Ti/Al/Ti/Αυ five-layer structure can be used. Preferably, the underlayer is made of a material having excellent adhesion to the current diffusion layer and having a thickness sufficient to avoid stress damage during contact with the metal layer or the current diffusion layer. • The outermost surface layer is preferably made of, for example, Au. Metal formation, which has excellent adhesion to the bonding ball. The transparent positive electrode of the present invention can be used without limitation in a conventionally known gallium nitride compound semiconductor light-emitting device, as shown in Fig. 1, the nitrogen The gallium compound semiconductor light-emitting device is formed by stacking a gallium nitride-based compound semiconductor on a substrate via a buffer layer, and forming an n-type semiconductor layer, a light-emitting layer, and a p-type semiconductor layer thereon. 1311818 - As far as the substrate is concerned, any well-known substrate material can be used without any limitation, such as including sapphire single crystal (Al2〇3: A plane, C plane, M plane and R plane), spinel single crystal (MgAl204) ), ΖηΟ single crystal, LiA102 single crystal, LiGa02 single crystal and MgO single crystal oxide single crystal, germanium single crystal, SiC single crystal, GaAs single crystal, A1N single crystal, GaN single crystal, and boron single crystal containing ZrB2. Incidentally, the planar orientation of the substrate is not particularly limited. The substrate can be a simple substrate or a chamfered substrate. The n-type semiconductor layer, the light-emitting layer, and the p-type semiconductor layer are widely used in various structures, and these widely used thin layers can be used. Although the ruthenium type semiconductor layer particularly uses a general carrier concentration, the transparent positive electrode of the present invention can be applied even to a p-type semiconductor layer having a relatively low carrier concentration such as about 1 X 1 〇 17cnT3. The gallium nitride-based compound semiconductor system is widely used for various compositions represented by the general formula AlxInyGai.x_yN (OS x < 1, OS y < 1, OS x + y < 1). For the gallium nitride-based compound semiconductor forming the n-type semiconductor layer and the p-type semiconductor layer, these are represented by the general formula AlxInyGai.x.yN (0Sx <1,0gy< 1,0 ® $ x + y<1) A wide range of semiconductors of various compositions can be used without any limitation. In order to emit light in the ultraviolet region, the active layer uses a composition having an indium concentration of about 10% or less. This concentration can be controlled by the well film thickness, the barrier layer composition, and the concentration of the active layer carrier. The method of growing the gallium nitride-based compound semiconductor is not particularly limited. Well-known methods for growing lanthanide nitride semiconductors such as MOCVD (Metal Organic Chemical Vapor Deposition), HVPE (Hydride Vapor Phase Epitaxy) -12-1311818, and MBE (Molecular Beam Epitaxy) methods can be employed. From the viewpoint of controlling film thickness properties and mass production, a preferred growth method is MOCVD. The MOCVD method uses hydrogen (H2) or nitrogen (N〇 as a carrier gas 'trimethylalkyl gallium (TmG) or triethylgallium (TEG) as a source of gallium for m-group materials, trimethyl aluminum oxide (TMA) or three Ethyl aluminum (TEA) is used as the aluminum source, trimethylalkyl indium (TMI) or triethylindium indium (TEI) as the indium source' and ammonia (NH3) or hydrazine (N2H4) as the nitrogen source of the Group V raw material. Monodecane (SiH4) or dioxane (Si 2H6) as a raw material of ruthenium and decane (GeH4) as a raw material of ruthenium are p-type dopants, such as dicyclopentadienyl magnesium (CpzMg) as a raw material for magnesium or Diethyl biscyclopentadienyl magnesium ((EtCp) 2Mg) is a P-type dopant. It is a negative electrode for forming an n-type semiconductor layer contacting a gallium nitride-based compound semiconductor (wherein the gallium nitride-based compound semiconductor) The light-emitting layer and the germanium-type semiconductor layer are partially removed to expose the n-type semiconductor layer by sequentially stacking the n-type semiconductor layer, the light-emitting layer, and the germanium-type semiconductor layer on the substrate. Second, the transparent positive of the present invention The electrode is formed on the remaining portion of the p-type semiconductor layer, and the negative electrode is formed on the exposed n-type semiconductor The negative electrode is widely used in various compositions and various structures. The widely used negative electrode can be used without any limitation. The present invention will now be more specifically described below with reference to examples. Example 1 : Fig. 2 is a schematic cross-sectional view showing a gallium nitride-based compound semiconductor ultraviolet light-emitting device manufactured by the present example, and Fig. 3 is a plan view schematically showing a buffer on a substrate 1 formed of sapphire via Α1Ν Layer 6 is stacked with 8-13- 1311818 micron thick GaN undoped underlayer 3a, 2 micron thick erbium-doped A1GaN contact layer 3b' 0.03 micron n-type inG1GaQ 9N cladding 3c, 16 nm thick sand doped The Al〇.iGac.9N barrier layer and the 4 nm thick Inu2Ga() 98n well layer are stacked on top of each of the five cycle parental faults, and finally the multi-quantum well structure of the barrier layer is provided with a light-emitting layer 4, 〇. 01 μm thick magnesium-doped p-type A1() Q7GaQ 93n cladding layer 5a and 0.15 micron thick magnesium-doped p-type AiGaN contact layer 5b are sequentially stacked thereon. On the p-type AlGaN contact layer of the gallium nitride-based compound semiconductor Stacked with a 1.5 nm thick platinum contact metal layer η and a 3 nm thick 铑 current diffusion The layer 12 is formed to form the positive electrode of the present invention. The Au/Ti/Al/Ti/Au five-layer structure is formed on the current diffusion layer (the thickness is 5〇/2〇/1〇/1〇〇/ 2 〇〇 nm) of the bonding pad layer 13. Secondly, the negative electrode 20 of the Ti/Au bilayer structure is formed on the n-type AiGaN contact layer to form a light-emitting device having a light-emitting plane at the semiconductor end. The positive electrode and the negative electrode The shape is as shown in Fig. 3. In this structure, the carrier concentration of the 'n-type AiGaN contact layer is ix1()'9cm-3, and the erbium doping mass in the AiGaN barrier layer is lxi〇i8cm-3, p-type AiGaN The carrier concentration of the contact layer was 5×10 18 cm −3 , and the mass of magnesium in the p-type AiGaN barrier layer was 5×10 019 cn T 3 . The stack of the gallium nitride-based compound semiconductor layer is carried out by MOCVD under conditions well known in the related art. The positive electrode and the negative electrode are formed in the following steps. First, a portion of the n-type AiGaN contact layer on which the negative electrode is formed by the reactive ion etching technique is exposed by the following steps. Initially, an etch mask is formed on the P-type semiconductor layer. This formation method is as follows. The photoresist is applied uniformly to the entire surface, and a region having a larger size than the positive electrode region is removed on the applied photoresist coating by the well-known micro- 14-1311818-shading technique. The masked p-type semiconductor layer was placed in a vacuum deposition apparatus, and nickel and titanium having a film thickness of 5 Onm and 300 nm were separately deposited thereon by electron beam technique under a pressure of 4 x 10 −4 Pa or less. Next, the metal film and the photoresist outside the positive electrode region are stripped by a stripping technique. Next, the semiconductor stacked substrate is mounted on an electrode in an etching chamber of the active ion etching apparatus, the etching chamber is compressed to 1 (Γ4 P a, chlorine gas is supplied into the chamber as an etching gas, and etching is continued to expose the n-type AlGaN. #Contact layer. After etching, the semiconductor stacked substrate is taken out by a reactive ion etching device, and the etching mask is removed with nitric acid and hydrofluoric acid. Secondly, the platinum is contacted with the metal layer by well-known lithography and stripping techniques. Formed separately from the erbium current diffusion layer in a region for forming a positive electrode on the P-type AlGaN contact layer. When forming the contact metal layer and the current diffusion layer, first, a gallium nitride-based compound semiconductor layer is stacked thereon The substrate is placed in a vacuum deposition chamber, and a thickness of 1.5 nm is deposited on the p-type AlGaN contact layer, and then a thickness of 3 nm is deposited. Therefore, the Φ positive electrode of the present invention is formed on the P-type AlGaN contact layer. The substrate formed by the vacuum chamber is taken out and processed according to a well-known procedure (commonly referred to as "stripping"). In addition, gold is stacked in a similar sequence. a first layer, a second layer formed of titanium, a third layer formed of aluminum, a fourth layer formed of titanium, and a fifth layer formed of gold, and a bonding pad layer is formed on a portion of the current diffusion layer. The present invention can avoid transparency The electrode portion contains gold, and gold is not observed in the bonding pad. Gold is a metal having excellent bonding properties. The formation of gold in the uppermost layer of the bonding pad is formed in a conventional manner. -15 - 1311818 Formed by the method The positive electrode is penetrable and has a light transmittance of 70% in a wavelength region of 405 nm. The light transmittance is judged by using a sample obtained by forming the same contact metal layer and current diffusion layer. Wherein the sample has a predetermined size for determining the light transmittance.
其次，根據下列步驟形成負電極於所暴露的η型AlGaN 接觸層上。將光阻劑均勻施加於整個表面，並藉由熟知的 微影技術在用於形成負電極於所暴露η型AlGaN接觸層上 的部位移除所施加的光阻劑塗佈物，以及藉由普遍使用的 真空沈積技術依序由半導體端沈積由100nm厚之鈦與200 nm 厚之金所組成的負電極。其次，以廣知的技術移除光阻劑 〇 具有前揭正電極與負電極形成於其上的晶圓具有基板 接地的第二表面，並拋光至80微米的基板厚度。其係使用 雷射刮刀而由半導體沈積端畫線。施壓將晶圓分割成3 5 0 微米見方的晶粒。當這些晶粒藉由暴露於以探針傳導的電 流而在20mA安培數的正向電壓進行後續測試時，該電壓 爲 2.9V » 其次，當晶片安裝於TO-1 8罐式封裝物並以測試機測 試發光輸出時，在20mA安培數下的發光輸出爲7mW。有 關發光平面上的發光分佈方面，其證實晶粒在整個正電極 表面上發光。 對照實例1 : 發光裝置係以實例1的步驟進行製造，且由Au/Nio 所形成的習用電極係形成於相同的氮化物半導體沈積基板 -16- 1311818Next, a negative electrode is formed on the exposed n-type AlGaN contact layer according to the following steps. Applying a photoresist uniformly to the entire surface, and removing the applied photoresist coating at a portion for forming a negative electrode on the exposed n-type AlGaN contact layer by well-known lithography techniques, and by A commonly used vacuum deposition technique sequentially deposits a negative electrode composed of 100 nm thick titanium and 200 nm thick gold from the semiconductor end. Next, the photoresist is removed by a well-known technique. The wafer having the front and back electrodes formed thereon has a second surface to which the substrate is grounded and polished to a substrate thickness of 80 μm. It uses a laser scraper to draw lines from the semiconductor deposition end. The pressure is divided into wafers of 3 50 μm square. When these dies were subsequently tested at a forward voltage of 20 mA amps by exposure to current conducted by the probe, the voltage was 2.9 V » Next, when the wafer was mounted on a TO-1 8 can package and When the tester tests the luminous output, the luminous output at 20 mA amperage is 7 mW. Regarding the distribution of light emission on the light-emitting plane, it was confirmed that the crystal grains emit light on the entire surface of the positive electrode. Comparative Example 1: The light-emitting device was fabricated in the procedure of Example 1, and the conventional electrode formed of Au/Nio was formed on the same nitride semiconductor deposition substrate -16-1311818
- 上。正向電壓與發光裝置的發光輸出分別爲2.9V及3.OmW 。當以肉眼觀察裝置的發光平面時，其係以類似於實例1 的方式在整個表面上發光。然而，接觸金屬層具有約40°/。 的透光率’因而被認爲會有發光輸出降低的問題。 本發明所提供之用於氮化鎵系化合物半導體發光裝置 的電極可作爲用於發出紫外光之透明氮化鎵系化合物發光 裝置的正電極。 【圖式簡單說明】 • 第1圖爲設有本發明透明正電極之發光裝置的橫剖面 示意圖。 第2圖爲設有實例1所製造之本發明透明正電極的氮 化鎵系化合物半導體發光裝置的橫剖面示意圖。 第3圖爲設有實例1所製造之本發明透明正電極的氮 化鎵系化合物半導體發光裝置的平面示意圖。 【主要元件符號說明】 1 基板 2 GaN系化合物半導體層 3 η型半導體層 3 a 未摻雜底層 3b 摻矽η型AlGaN接觸層 3 c η 型 I η 〇. 1 G a。9 N 覆層 4 發光層 5 p型GaN系化合物半導體層 5 a 摻鎂P型AlQ.Q7GaQ.93N覆層 -17- 1311818 5b 摻 鎂 P 型 AlGaN接觸層 6 緩 衝 層 10 透 明 正 電 極 11 接 觸 金 屬 層 12 電 流 擴 散 層 13 接 合 墊 層 20 負 電 極- On. The forward voltage and the illuminating output of the illuminating device are 2.9V and 3.OmW, respectively. When the light-emitting plane of the device was observed with the naked eye, it was illuminated on the entire surface in a manner similar to that of Example 1. However, the contact metal layer has about 40°/. The light transmittance 'is thus considered to have a problem that the light output is lowered. 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 transparent gallium nitride-based compound light-emitting device for emitting ultraviolet light. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic cross-sectional view showing a light-emitting device provided with a transparent positive electrode of the present invention. Fig. 2 is a schematic cross-sectional view showing a gallium nitride-based compound semiconductor light-emitting device provided with the transparent positive electrode of the present invention produced in Example 1. Fig. 3 is a plan view schematically showing a gallium nitride-based compound semiconductor light-emitting device provided with the transparent positive electrode of the present invention produced in Example 1. [Description of main component symbols] 1 substrate 2 GaN-based compound semiconductor layer 3 n-type semiconductor layer 3 a undoped underlayer 3b ytterbium-doped n-type AlGaN contact layer 3 c η type I η 〇. 1 G a. 9 N cladding 4 luminescent layer 5 p-type GaN-based compound semiconductor layer 5 a magnesium-doped P-type AlQ.Q7GaQ.93N cladding -17- 1311818 5b magnesium-doped P-type AlGaN contact layer 6 buffer layer 10 transparent positive electrode 11 contact metal Layer 12 current diffusion layer 13 bonding pad 20 negative electrode
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