1297222 九、發明說明： 【發明所屬之技術領域】 本發明係關於氮化嫁系發光二極體裝置，尤其是有關於 一種以IZO材料構成歐姆接觸層以提高光取出效率的氮化鎵 系發光二極體裝置的結構與製造方法。 【先前技術】 氮化鎵（GaN)系發光二極體，由於可以藉著控制材料 的組成來製作出各種色光的發光二極體，其相關技術因此成 為近年來發光二極體的主流技術。目前習知的氮化鎵系發光 二極體多是以III-V族的氮化鎵系化合物半導體來形成p-n介 面’然後藉由對發光二極體施加一適當的順向直流電壓，驅 使發光二極體的電子、電洞結合而釋放出光子。 氮化鎵系發光二極體的發光效率，主要和氮化鎵系發光 二極體的内部量子效率（Internal Quantum Efficiency)以及外 部量子效率（External Quantum Efficiency )有關。前者和氮 化鎵系發光二極體裡電子電洞結合進而釋放出光子的機率有 關。電子電洞愈容易復合，光子愈容易產生，内部量子效率 就愈高。後者則和光子不受氮化鎵系發光二極體本身的吸收 與影響、成功脫離氮化鎵系發光二極體的機率有關。愈多光 子能釋放到氮化鎵系發光二極體之外，外部量子效率就愈 高，因此也稱為光取出效率（lightextractionefficiency)。 影響氮化鎵系發光二極體的光取出效率的因素很多，其 5 1297222 中之一就是和氮化鎵系發光二極體的上層結構有關。氮化鎵 系發光二極體為了與外部電路建立電氣連結，一般均會於其 頂端设置至少一金屬電極（electrode)，而為了使金屬電極和 ΠΙ V族的氮化鎵系化合物半導體之間形成歐姆接觸，一般會 金屬電極之下先5又置一層歐姆接觸層（ohmic contact layer )此馱姆接觸層除了要有極低的電阻、高溫度穩定性 外，還要有高透光性（transmittance)以提高氮化鎵系發光二 極體的光取出效率。 產學界已經揭露了許多有關歐姆接觸層的技術。舉例而 吕，ITO (indium tin oxide)就是一個被廣泛採用的歐姆接觸 層材料。但是實驗顯示，ΓΓΟ雖有相當好的透光性，但仍有 相當的肖特基（Schottky )特性。另外一方面，IZ〇( indium 〇xide doped zinc oxide)是一種和ΓΓΟ類似具有高透光性且良好導 電性的氧化物材料。但和ιΤ〇相比較，其功函數（w〇rk function)要比ITO高約〇.6eV。近年來有相當多有關IZ(3的 研究，例如 Lim 等人的論文 Low-resistivity and Transparent Indium-oxide_doped ZnO Ohmic Contact to P-type GaN (發表 於 Allied Physics Letters，Volume 85, Number 25, 20 November 2004)，指出以3wt%Iri2〇3摻雜的ZnO材料，以蒸鍍方式在 P型氮化鎵系半導體上形成透明歐姆接觸層，再於6〇〇〇C氮 氣環境下合金五分鐘，可以達到光穿透率84%〜92%，和傳統 6 1297222 以Ni/Au金屬薄膜做成透明電極的70〜80%光穿透率相比，有 相當大的改善。但是實驗也發現，依此方式形成的氮化鎵系 發光二極體，其在20mA注入電流（injection current)下的 順向電壓（Vf〜4.3V)，和採用Ni/Au透明金屬電極的氮化鎵 系發光二極體相比，要高了約0.75V。 【發明内容】 因此，本發明提出一種以IZO材料構成歐姆接觸層的氮 化鎵系發光二極體裝置的結構與製造方法，除了具有高透光 性、能與金屬電極形成良好的歐姆接觸之外，還同時具有較 習知技術更為優良的電氣特性。 本發明所提出的氮化鎵系發光二極體裝置，包含由下而 上依序堆疊的一基板、一包含有p-n介面的發光結構、一由 金屬奈米顆粒構成的導電層、以及一 IZ0歐姆接觸層。其中， 導電層的厚度需不超過1000A以免影響光取出效率，其材料 可用金、鎳或類似的貴重金屬以化學成長或蒸鍍的方式形 成。IZ0歐姆接觸層則是由適當的IZ0材料先以濺鍍方式形 成至一適當厚度後再予以合金處理。在本發明的一實施例 中，IZ0材料可以是組成比9:1的Zn0:ln203，其厚度約為 2400A。合金處理則是在氮氣環境下，以300〜600°C的溫度 合金十分鐘。 茲配合所附圖示、實施例之詳細說明及申請專利範圍， 1297.222 將上述及本發明之其他目的與優點詳述於後。然而，當可了 解所_減係為職本發明之料而設，Μ視為本發明 範蜂之定義。有關本發明範4之定義，請參照所附之申請專 利範圍。 .【實施方式】 本發明提出一種以IZO材料構成歐姆接觸層以提高光取 出效率的鼠化鎵系發光二極體裝置的結構與製造方法。本說 月書所稱「氮化鎵系發光二極體裝置」係指具有以m—V族的 氮化鎵系化合物半導體構成p_n介面的發光二極體裝置。其 中III-V族的氮化鎵系化合物半導體的成分可以用以下的分 子式表示· InxAlyGai-x-yN (OSxSl，x+y$i )。此外，本說明 書所稱「透光性」係指其光穿透率至少在1%以上，而非限定 其為無色或透明。 第la圖所示係依據本發明所提出方法的第一個步驟所得 到的成品的剖面示意圖。如圖所示，本方法的第一個步驟係 提供一氮化鎵系發光二極體的磊晶結構（epitaxial structure)。此磊晶結構係至少包含一基板1〇、以及位於基板 10 —面之上的發光結構（light generating structure) 20。本發 明並不特別限定基板10與發光結構20的材料、以及發光結 構20的構成方法，任何習知的技術都可以採用。舉例而言’ 基板10是c-plane sapphire (藍寶石），而發光結構20是由適 1297222 當組成的InxAlyGa^-yN以金屬有機化學氣相沈積法 (metal-organic chemical-vapor deposition)幵》成。發光結構 20至少包含一 p型氮化鎵系化合物半導體層（以下稱p-GaN 層）22以及一 n型氮化鎵系化合物半導體層（以下稱nu(}aN 層）24以構成p-n介面。如圖所示，一般p_GaN層係位於n-GaN 層之上’但本發明並不特別設限。本發明同樣可以應用於 n-GaN層位於p_GaN層之上的發光結構，不過以下為了簡化 起見，主要以前者為例說明。 第lb圖所示係依據本發明所提出方法的第二個步驟所 得到的成品的剖面示意圖。如圖所示，本方法的第二個步驟 係在發光結構20之上用適當的金屬奈米顆粒 (nano dot particle)形成一導電層3〇。導電層3〇的厚度需不超過1〇〇〇a 以免影響光取出效率，其材料可用金（Au)、鎳（Ni)或類似 的貝重金屬以化學成長或蒸鍍（evaporation )的方式形成。 請注意到導電層3〇的設置並非絕對必要的，不過經實驗驗證 此導電層30的設置可以顯著改善本發明所產生的氮化鎵系 發光二極體裝置的電氣特性。 第10圖所示係依據本發明所提出方法的第三個步驟所得 到的成品的剖面示意圖。如圖所示，本方法的第三個步驟係 在導電層30之上形成一 ιΖ〇歐姆接觸層4〇。IZ〇歐姆接觸 層4〇疋由適當的IZ0材料，亦即以適當份量的InxOy( X，y21) 1297222 摻雜到ZnO裡，然後成長至一適當厚度後再予以合金 (annealing )處理。在本發明的一個實施例裡，IZO材料是 組成比9:1的ZnO:In2〇3，其係以藏鐘（sputtering)方式形成 約為2000〜3000A的厚度。合金處理則採一快速熱合金系統 (rapid thermal annealing system )在氮氣環境下，以 300〜600QC的溫度合金十分鐘。 請注意到，如果所製作的係具有水平結構的氮化鎵系發 • 光二極體裝置（也就是發光二極體的二個電極位於同一側）， 那麼在濺鍍與合金處理兩個步驟之間，可以如第Id圖所示， 先以蝕刻的方法使部分的n-GaN層暴露出來（以便後續於其 上實施η型電極），然後再進行合金處理。至此，本發明所提 出的氮化鎵系發光二極體裝置的結構基本上已經完成。接下 來，如第2c、或2d圖所示的架構，通常都會經過一個晶片製 程（chip process)將發光二極體裝置的p型電極與η型電極 • 在適當的位置處以適當的習知技術實施出來（例如第Id圖所 示的虛線元件），以下就不贅述。 和習知的技術比較，本發明所製作的氮化鎵系發光二極 體裝置具有顯著的優點。根據實驗顯示，本發明的IZO歐姆 接觸層在可見光的穿透率約為90%，而且用不同溫度合金所 得到的結果，其穿透率並沒有太大的變化，因此其溫度穩定 性很高。對於以金奈米顆粒所形成的導電層，第2a圖所示係 1297222 在不同溫度合金所得到IZO歐姆接觸層之特徵接觸電阻。如 圖所示，在 500QC 下合金之特徵接觸電阻約為 1·4χ10·4Ω-(：πι2。同樣以金奈米顆粒所形成的導電層、以及 500°C下合金的IZO歐姆接觸層為例，第2b圖所示係依據本 發明的氮化鎵系發光二極體裝置的Ι-V特性曲線。如圖所示， 在20mA的注入電流下，順向電壓約為3.5 IV，要比習知技術 的4.3V優異許多。 • 藉由以上較佳具體實施例之詳述，係希望能更加清楚描 述本創作之特徵與精神，而並非以上述所揭露的較佳具體實 施例來對本創作之範疇加以限制。相反地，其目的是希望能 涵蓋各種改變及具相等性的安排於本創作所欲申請之專利範 圍的範疇内。 【圖式簡單說明】 第la圖所示係依據本發明所提出方法的第一個步驟所得到的 W 成品的剖面示意圖。 第lb圖所示係依據本發明所提出方法的第二個步驟所得到 的成品的剖面示意圖。 第lc圖所示係依據本發明所提出方法的第三個步驟所得到的 成品的剖面示意圖。 第Id圖所示係依據本發明所提出方法的第三個步驟所得到 的另一成品的剖面示意圖。 1297222 第2a圖所示係在不同溫度合金所得到IZO歐姆接觸層之特徵 接觸電阻。 第2b圖所示依據本發明的氮化鎵系發光二極體裝置的I-V特 性曲線。 【主要元件符號說明】 10 基板 20 發光結構 22 p-GaN 層 24 n-GaN 層 30 導電層 40 IZO歐姆接觸層 12BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nitride-grafted light-emitting diode device, and more particularly to a gallium nitride-based light-emitting device in which an ohmic contact layer is formed of an IZO material to improve light extraction efficiency. The structure and manufacturing method of the diode device. [Prior Art] A gallium nitride (GaN)-based light-emitting diode has a light-emitting diode of various color lights by the composition of a control material, and the related art has become a mainstream technology of light-emitting diodes in recent years. At present, a conventional gallium nitride-based light-emitting diode is formed by a III-V gallium nitride-based compound semiconductor to form a pn interface, and then an appropriate forward DC voltage is applied to the light-emitting diode to drive light. The electrons and holes of the diode combine to release photons. The luminous efficiency of the gallium nitride-based light-emitting diode is mainly related to the internal quantum efficiency (Internal Quantum Efficiency) of the gallium nitride-based light-emitting diode and the external quantum efficiency (External Quantum Efficiency). The former is related to the probability of combining electron holes in the gallium nitride-based light-emitting diode to release photons. The easier the electron hole is recombined, the easier the photon is, and the higher the internal quantum efficiency. The latter is related to the probability that the photon is not absorbed and affected by the gallium nitride-based light-emitting diode itself and is successfully separated from the gallium nitride-based light-emitting diode. The more photons can be released into the gallium nitride-based light-emitting diode, the higher the external quantum efficiency, so it is also called lightextraction efficiency. There are many factors affecting the light extraction efficiency of the gallium nitride-based light-emitting diode, and one of the 5 1297222 is related to the upper structure of the gallium nitride-based light-emitting diode. In order to establish an electrical connection with an external circuit, the gallium nitride-based light-emitting diode generally has at least one metal electrode disposed at the top end thereof, and is formed between the metal electrode and the ΠΙV group gallium nitride-based compound semiconductor. Ohmic contact, generally under the metal electrode, first placed an ohmic contact layer. In addition to the extremely low resistance and high temperature stability, the ohmic contact layer also has high transparency (transmittance). ) to improve the light extraction efficiency of the gallium nitride-based light-emitting diode. The industry has exposed many techniques related to ohmic contact layers. For example, ITO (indium tin oxide) is a widely used ohmic contact layer material. However, experiments have shown that although it has a fairly good light transmission, it still has considerable Schottky characteristics. On the other hand, indium idexide doped zinc oxide is an oxide material which has high light transmittance and good electrical conductivity similar to ruthenium. However, compared with ιΤ〇, its work function (w〇rk function) is about 〇.6eV higher than ITO. In recent years, there have been quite a few studies on IZ (3, such as Lim-resistivity and Transparent Indium-oxide_doped ZnO Ohmic Contact to P-type GaN (published in Allied Physics Letters, Volume 85, Number 25, 20 November 2004). ), indicating that a ZnO material doped with 3 wt% Iri2〇3 forms a transparent ohmic contact layer on the P-type gallium nitride-based semiconductor by vapor deposition, and then alloys in a nitrogen atmosphere of 6 〇〇〇C for five minutes. The light transmittance is 84%~92%, which is quite improved compared with the traditional 6 1297222 70~80% light transmittance of the transparent electrode made of Ni/Au metal film. However, the experiment also found that in this way The formed gallium nitride-based light-emitting diode has a forward voltage (Vf to 4.3V) at an injection current of 20 mA, and a gallium nitride-based light-emitting diode phase using a Ni/Au transparent metal electrode Therefore, the present invention proposes a structure and a manufacturing method of a gallium nitride-based light-emitting diode device in which an ohmic contact layer is formed of an IZO material, in addition to having high light transmittance and energy. Formed with a metal electrode In addition to good ohmic contact, it also has more excellent electrical characteristics than the prior art. The gallium nitride-based light-emitting diode device of the present invention comprises a substrate stacked sequentially from bottom to top, and a a light-emitting structure having a pn interface, a conductive layer composed of metal nanoparticles, and an IZ0 ohmic contact layer, wherein the thickness of the conductive layer is not more than 1000 A so as not to affect light extraction efficiency, and the material may be gold, nickel or the like. The precious metal is formed by chemical growth or evaporation. The IZ0 ohmic contact layer is formed by sputtering the appropriate IZ0 material to a suitable thickness and then alloying. In an embodiment of the invention, the IZ0 material It may be a composition ratio of 9:1 Zn0: ln 203, and its thickness is about 2400 A. The alloy treatment is in a nitrogen atmosphere at a temperature of 300 to 600 ° C for ten minutes. The drawing is accompanied by the detailed description of the embodiment. DESCRIPTION AND APPLICATIONS Scope, 1297.222 The above and other objects and advantages of the present invention will be described in detail later. However, it can be understood that the present invention is based on the material of the present invention. Definition of Van Bee. For the definition of the invention, please refer to the attached patent application scope. [Embodiment] The present invention provides a murine gallium-based light-emitting diode which is formed of an IZO material to form an ohmic contact layer to improve light extraction efficiency. The structure and manufacturing method of the polar body device. The "gallium nitride-based light-emitting diode device" referred to in the monthly book refers to a light-emitting diode device having a p-n interface formed of a m-V group gallium nitride-based compound semiconductor. . The composition of the III-V group gallium nitride-based compound semiconductor can be expressed by the following molecular formula: InxAlyGai-x-yN (OSxSl, x+y$i). Further, "transparency" as used in this specification means that the light transmittance is at least 1% or more, and it is not limited to being colorless or transparent. Figure la is a schematic cross-sectional view of the finished product obtained in accordance with the first step of the method of the present invention. As shown, the first step of the method provides an epitaxial structure of a gallium nitride based light emitting diode. The epitaxial structure comprises at least a substrate 1 and a light generating structure 20 located above the substrate 10. The present invention is not particularly limited to the material of the substrate 10 and the light-emitting structure 20, and the method of constructing the light-emitting structure 20, and any of the conventional techniques can be employed. For example, 'the substrate 10 is c-plane sapphire (sapphire), and the light-emitting structure 20 is made of a metal-organic chemical-vapor deposition method composed of InzAlyGa^-yN composed of 1297222. . The light-emitting structure 20 includes at least a p-type gallium nitride-based compound semiconductor layer (hereinafter referred to as p-GaN layer) 22 and an n-type gallium nitride-based compound semiconductor layer (hereinafter referred to as nu(}aN layer) 24 to constitute a pn interface. As shown in the figure, the general p_GaN layer is located on the n-GaN layer', but the invention is not particularly limited. The invention can also be applied to the light-emitting structure in which the n-GaN layer is on the p-GaN layer, but the following is simplified. See, the main former is an example. Figure lb shows a schematic cross-sectional view of the finished product obtained according to the second step of the proposed method. As shown, the second step of the method is in the light-emitting structure. A conductive layer 3 is formed on top of 20 with appropriate nano dot particles. The thickness of the conductive layer 3〇 is not more than 1〇〇〇a so as not to affect the light extraction efficiency, and the material can be made of gold (Au), Nickel (Ni) or a similar shellfish metal is formed by chemical growth or evaporation. Note that the setting of the conductive layer 3〇 is not absolutely necessary, but it has been experimentally verified that the arrangement of the conductive layer 30 can significantly improve the present. Invention office The electrical characteristics of the raw gallium nitride-based light-emitting diode device. Figure 10 is a schematic cross-sectional view of the finished product obtained according to the third step of the method of the present invention. As shown, the third method of the method The steps are to form an ohmic ohmic contact layer 4 on the conductive layer 30. The IZ ohmic contact layer 4 is doped to the ZnO by a suitable IZ0 material, that is, an appropriate amount of InxOy (X, y21) 1297222. Then, it is grown to an appropriate thickness and then subjected to an alloying treatment. In one embodiment of the invention, the IZO material is a composition ratio of 9:1 ZnO:In2〇3, which is in a sputtering manner. A thickness of about 2000 to 3000 A is formed. The alloy is treated with a rapid thermal annealing system in a nitrogen atmosphere at a temperature of 300 to 600 QC for ten minutes. Note that if the system is made to have a level The structure of the gallium nitride-based light-emitting diode device (that is, the two electrodes of the light-emitting diode are located on the same side), then between the two steps of sputtering and alloy processing, as shown in Figure Id, Etched The method exposes a portion of the n-GaN layer (to subsequently perform an n-type electrode thereon) and then performs alloy processing. Thus, the structure of the gallium nitride-based light-emitting diode device proposed by the present invention has been substantially completed. Next, as in the architecture shown in Figure 2c or 2d, the p-type electrode and the n-type electrode of the light-emitting diode device are usually passed through a chip process. The technology is implemented (for example, the dotted line element shown in the figure Id), and will not be described below. The gallium nitride based light emitting diode device produced by the present invention has significant advantages as compared with conventional techniques. According to experiments, the IZO ohmic contact layer of the present invention has a transmittance of about 90% in visible light, and the transmittance obtained by using different temperature alloys does not change much, so the temperature stability is high. . For the conductive layer formed by the gold nanoparticles, the characteristic contact resistance of the IZO ohmic contact layer obtained by the alloy 1297222 at different temperatures is shown in Fig. 2a. As shown in the figure, the characteristic contact resistance of the alloy at 500QC is about 1·4χ10·4Ω-(:πι2. The same is also the conductive layer formed by the gold nanoparticles and the IZO ohmic contact layer of the alloy at 500 °C. Figure 2b is a Ι-V characteristic curve of the gallium nitride-based light-emitting diode device according to the present invention. As shown in the figure, at a current of 20 mA, the forward voltage is about 3.5 IV. The 4.3V of the prior art is much better. • The features and spirit of the present invention are more clearly described by the detailed description of the preferred embodiments above, and the present invention is not limited to the preferred embodiments disclosed herein. The scope is limited. Conversely, the purpose is to cover various changes and equivalences within the scope of the patent application to which the present application is intended. [Simplified Schematic] Figure la is shown in accordance with the present invention. A schematic cross-sectional view of the finished product obtained by the first step of the method is proposed. Figure lb is a schematic cross-sectional view of the finished product obtained according to the second step of the proposed method of the present invention. Place A schematic cross-sectional view of the finished product obtained by the third step of the method is proposed. Figure Id is a schematic cross-sectional view of another finished product obtained according to the third step of the method of the present invention. 1297222 Figure 2a is shown in Figure 2a The characteristic contact resistance of the IZO ohmic contact layer obtained by different temperature alloys. Fig. 2b shows the IV characteristic curve of the gallium nitride based light-emitting diode device according to the present invention. [Main element symbol description] 10 substrate 20 light-emitting structure 22 p -GaN layer 24 n-GaN layer 30 conductive layer 40 IZO ohmic contact layer 12