1231055 狄、發明說明 【發明所屬之技術領域】 本發明是有關於一種氮化鎵系發光二極體之製造 方法與結構，且特別是一種可提高發光亮度，以及= 有靜電放電防護之氮化鎵系發光二極體的製作方法與 結構。 、 【先前技術】 發光二極體（Light Emitting Diode ; LED)因具有生 產成本低、結構簡單、低耗電、體積小以及安裝容易 之優勢’而大量運用於照明光源以及顯示器技術中。 其中，又以類屬氮化鎵系（Gallium Nitride-based ; GaN-based)的發光元件，例如氮化鎵（GaN)藍光發光二 極體，在近幾年的發光元件市場中，甚受重視。 一般的氮化鎵系發光二極體，基於氮化鎵系臈層 之結晶品質的考量，大多選用藍寶石（sapphire)材質作 為基板。然而’由於藍寶石係為一絕緣材料，因此， 使得元件中的陽極電極與陰極電極須製作於藍寶石基 板的同一面上，而導致電流傳送時，容易於陰極附近 發生電流擁擠（current crowding)的現象，使操作電阻 增加，以致降低了光輸出的效率。 另外，藍寳石的絕緣性質，亦無法對於元件製作 中產生的靜電累積’提供有效的導通釋放，因此極容 易導致靜電放電（Electro_Static Discharge ; ESD)的問 1231055 材質 ，而 題發生，而對元件造成損壞。同時，因為藍寳石 的散熱性不佳，亦會導致元件運作過熱的現象產生 降低了發光元件之運作效能。 际g <外’元件之亮度提升，是目前發光二極體 技術的主要發展趨勢，但是，由於藍寶石基材會部分 吸收兀件之發光，纟對於元件之發光所具有的反射率 極低’例如對藍光的反射率約只有2%〜7%。因此，氮 化鎵系發光元件的光輸出強度係完全取決於二極體本 身的發光特性，而無法另外將二極體發出的光作有效 地利用，以使元件的光輸出強度獲得提升。 【發明内容】 本發月之目的之一是在提供一種氮化鎵系 (GaN-based)發光二極體之製作方法與結構，不但可以改 善元件内的電流分散情形，以提升發光二極體的光輸出效 率更利用對70件之發光的有效利用，而大幅增強光輸出 的強度’進而提高元件的品質與亮度呈現。 田另外，本發明之另—目的，亦可降低元件内的靜電累 積量乂有效避免靜電放電的問題發生，而減少靜電對元 件造成之損害。 根據本發明之上述目的，提出一種氮化鎵系發光二極 體之製作方法與結構。依照本發明之方法係為在基板上先 /、人^氮化鎵系發光兀件’其中，氮化鎵系發光元件 内…第-電性氮化鎵系半導體層、發光主動層、第二 1231055 電性氮化鎵系半導體層、透明導電層、第—電性電極與第 :電性電極’而基㈣例如為藍寳石基材，以獲得結晶品 、良子的氮化鎵系半導體層。接著，貼附—暫時載體於氮 化鎵系發光元件之上’且暫時載體與氮化鎵系發光元件之 間’係包含-用以接合暫時載體與氮化鎵系發光元件之黏 膠層然後’將基板移除’以完整暴露出氮化鎵系發光元 件之第一電性氮化鎵系半導體層。 接著，再依序形成一反射層與金屬基材層於第一電性 氮化鎵系半導體層之上’最後，將暫時載體與黏膠層同時 移除，而完成具有金屬導電基板的氮化鎵系發光二極體。 其中，氮化鎵系發光元件例如可為氮化鎵（GaN)二極 體，而反射層係選用對藍紫綠光具有高反射特性之金屬材 質，例如銀（Ag)或鋁（A1)，可反射氮化鎵系二極體之部分 發光，以提高氮化鎵系元件之光輸出強度。另外，金屬基 材層則為具有良好導電特性之金屬材質，例如銀或銅 (Cu)，可提供為元件内電流分散的流通路徑，而提升電流 分散的成效，減少電流擁擠的現象，並降低元件的操作電 阻，進而增加元件的光輸出效率。 同時’對於一些在製程進行中產生於元件内的靜電累 積量’更可藉由具導電特性之金屬基材層而予以導通釋 放’以有效避免靜電放電的問題發生。除此之外，通常導 電金屬基材亦具有良好的熱傳性，因此，有助於增加元件 的散熱性’而提供發光元件操作時極佳的散熱效果，以保 有元件的運作效能。 1231055 因此’應用本發明之氮化鎵系發光二極體的製作方 法，除了以反射層之設置，對元件内部之發光作有效之利 用’而大幅提升元件的光輸出強度之外，更利用將基板置 換為導電性佳的金屬基材，而改善元件内的電流分散成 效’以使7G件之操作電阻降低，並進而提升元件之光輸出 效率。另外，因元件内靜電累積而導致靜電放電傷害之問 亦可藉由導電性金屬基材而有效避免。故藉由本發明 之方法所製作的氮化鎵系發光二極體，不僅因光輸出強度 以及光輸出效率之增加，而大幅提升了元件的亮度，同 時，更因降低了元件受靜電放電傷害之機率，而增加了氮 化鎵系發光元件製作之產品良率與可靠度。 【實施方式】 本發明係提供一種氮化鎵系（GaN-based)發光二極體 之製作方法與結構，以轉移基板之技術，將製作於藍寶石 基材上的氮化鎵系發光二極體，移轉至金屬基板上，藉由 金屬基板的導電性，以提供元件良好的電導通作用，進而 提升元件内的電流分散效果，並降低元件内的靜電累積 量。同時，於金屬基板與氮化鎵系發光二極體之間，設置 有一反射層，利用反射層對光所具有的高反射特性，以使 二極體之發光，可有效地被反射而成為光輸出的另一來 源，進而提高元件之光輸出強度。以下將以實施例對本發 明之方法加以詳細說明。 1231055 實 本發明揭露了一種氮化鎵（GaN)發光二極體之製作方 法與結構。依序參照第1A〜1E圖，第1A〜1E圖係為依照 本發明較佳實施例之一種氮化鎵發光二極體製作方法的 流程剖面示意圖。 在第1A圖中，首先製作一具有基板1〇〇的氮化錁二 極體元件U0，其中，基板10〇例如選用藍寶石（sapphire) 材質，以獲得結晶品質良好的氮化鎵半導體層，而氮化鎵 二極體元件110的製作，首先係分別依序形成一 η型氮化 錄半導體層102, 一具有多層量子井（Multi_Quantum WeU) 結構之發光主動層104，以及一 p型氮化鎵半導體層ι〇6 於基板100之上。接著，在p型氮化鎵半導體層ι〇6之上， 形成一透明導電層108，以提供電流分散（current spreading)之作用，透明導電層1〇8的材質則例如可為銦 錫氧化物（Indium-Tin Oxide ; ITO)或錮鋅氧化物 (Indium-Zinc Oxide ; IZ0)。然後，分別在透明導電層108 以及η型氮化鎵半導體層ι〇2之部分表面上，形成陽極電 極112與陰極電極丨丨4。 接著’參照第1B圖，利用一黏膠層116，先將製作 於基板1 〇〇上的氮化鎵二極體元件丨i 〇，整個結構倒置地 貼附於一暫時載體120之上。其中，黏膠層116例如可使 用環氧樹脂（epoxy)或瞬間接著膠。然後，將基板1〇〇移 除，以暴露出完整的η型氮化鎵半導體層102,如第1C 圖所示，而移除基板1 〇〇的方法則例如可採用雷射剝離 1231055 (laser lift-off)或是研磨技術。 參照第1D圖，在移除基板1 〇 〇之後，以接合的方 式，依序形成一反射層130以及一金屬基材層140於！! 型氮化鎵半導體層之上，其中，反射層130係選用對紫藍 綠光波長範圍之發光具有高反射率的金屬材質，例如可為 銀（Ag)、鋁（Α1)、鎳（Ni)、把（Pd)或鉬（Mo)，尤其是銀或 崔呂具有的反射率約達85%〜90%。金屬基材層140則選用 導電性佳的金屬材質，例如可為銀或銅（Cu),且金屬基材 層140的厚度明顯大於反射層13〇的厚度，以提供作為支 撐氮化鎵發光二極體的導電性基板。 最後，再將黏膠層11 6移除，以同時分離暫時載體 120，而形成一具有金屬基材層14〇的氮化鎵二極體元件 150，如第1E圖所示。氮化鎵二極體元件ι5〇，係以具有 良妤導電性的金屬基材層140作為承載基板。 在第1E圖中，由於反射層130具有的高反射特性， 可使元件内的發光，除了一部份直接向上輸出之外，另一 部份朝向金屬基材層140發出的光，則藉由反射層13〇 的反射作用，而提供成為向上輸出的光源，使元件内的發 光能被有效地再次利用，以增加元件可達成的光輸出強 度。 另外，可藉由金屬基材層140所提供的良好導電特 性，而使元件内的電流傳遞，由陽極電極丨12的位置，往 下分散時，先流經金屬基材層14〇，再往陰極電極114的 位置傳送，如此，可形成電阻並聯降低阻值的效應，並改 1231055 善當陰極電極H2與陽極電極114製作於同—平面時， 易產生於η型氮化鎵半導㈣1G2附近的電流了 (current Crowding)現象，因而，有效降低元件的操作 阻’進而提高元件的光輸出效率。 除此之外，對於一些在製程進行中產生於元件内的靜 電累積量，更可藉由具導電特性之金屬基材層14〇而庐得 導通釋放’以有效避免靜電放電CElectro-S^ Dis·㈣ESD)的問題發生，進而降低元件受損的機率。 另外，由於反射層Π0選用之金屬材質亦具有導電特 性，故亦可於氮化鎵二極體結構製作時（如第丨入圖所 示），先不製作陰極電極114,而於基板轉移完成之後， 移除部分之η型氮化鎵半導體層1G2,再將陰極電極ιΐ4 製作於反射層130之上，完成如第2圖所示之另一發光二 極體結m件内之電流傳送情形，即為電流傳遞路徑 220所表示。>此，更可有*避免電流擁擠現象發生於n 型氣化料導體| 1()2之位置以或者是亦可將陰極電極 U4直接製作在金屬基材層14〇之下方，以形成垂直電流 之電流分佈情形，而大幅提昇電流分散之成效。 根據上述本發明之實施例可知，應用本發明之氮化鎵 發光二極體的製作方法，可在不影響一般元件的製作條件 下、’利用元件基板轉移的技術，將原本的絕緣性基板，轉 換為導電性佳的金屬基板，以同時提高元件内電流傳遞分 散的效率，並降低靜電放電的危害產生，進而提升氮化鎵 元件的光輸出效率以及元件製造的產品良率。另外，通常 12 1231055 導電金屬基材亦具有良好的熱傳性，因此，有助於增加元 件的散熱性，而提供發光元件操作時極佳的散熱效果，以 保有元件的運作效能。 本發明亦利用反射層，對氮化鎵元件之發光具有高反 射的能力，以使元件内的發光可有效地被利用，將原本非 直接向外輸出的部分發光，經由反射層的反射作用，而轉 換成為元件實際之輸出光源的一部份，因此大幅增加了氮 化鎵元件的光輸出強度，進而提升元件的亮度呈現。 本發明不只侷限於使用在氮化鎵發光二極體的技術 上，其他所有屬於氮化鎵系發光二極體元件之製作，例如 氮化錮鎵（InGaN)發光二極體或氮化鋁鎵（A1GaN)紫外光 發光二極體，亦可藉由本發明之方法製作，而大幅提升產 品的特性。 雖然本發明已以實施例揭露如上，然其並非用以限 =本發明，任何熟習此技藝者，在不脫離本發明之精神和 範圍内’當可作各種之更動與修飾，因此本發明之保護範 圍當視後附之申請專利範圍所界定者為準。 【圖式簡單說明】 為讓本發明之上述特徵、 .^ ^ ^ 行徵方法目的及優點能更明顯 易Μ，配合所附圖式，加以說明如下： 第1Α〜1Ε圖係為依照本發明較佳實施 鎵發光二極體製作方、土从種氣化 ^ 腹表作方法的流程剖面示意圖。 弟2圖係為依照本 4费a罕乂住貫施利之另一氮化鎵發 13 1231055 光二極體結構示意圖。 【元件代表符號簡單說明】 100 :基板 102、106 :氮化鎵半導體層 104 ··主動層 108 :透明導電層 110、150 ·•二極體元件 11 2、114 :電極 11 6 :黏膠層 120 :載體 130 :反射層 140 ··金屬基材層1231055 D. Description of the invention [Technical field to which the invention belongs] The present invention relates to a method and structure for manufacturing a gallium nitride-based light emitting diode, and in particular to a nitride that can improve luminous brightness and = have electrostatic discharge protection Manufacturing method and structure of gallium-based light emitting diode. [Previous Technology] Light Emitting Diodes (LEDs) are widely used in lighting sources and display technologies because they have the advantages of low production cost, simple structure, low power consumption, small size, and easy installation. Among them, Gallium Nitride-based (GaN-based) light-emitting devices, such as gallium nitride (GaN) blue light-emitting diodes, have received much attention in the light-emitting device market in recent years. . In general, GaN-based light-emitting diodes are based on the crystalline quality of the GaN-based hafnium layer, and most of them use sapphire as the substrate. However, because sapphire is an insulating material, the anode electrode and cathode electrode in the element must be made on the same side of the sapphire substrate. As a result, current crowding easily occurs near the cathode when the current is transmitted. , So that the operating resistance is increased, so that the efficiency of light output is reduced. In addition, the insulating nature of sapphire cannot provide effective conduction release for the static electricity generated during the production of components. Therefore, it is extremely easy to cause electrostatic discharge (Electro_Static Discharge; ESD). damage. At the same time, the poor heat dissipation of sapphire will also lead to overheating of the components, which will reduce the performance of the light-emitting components. The improvement of the brightness of the external element is the main development trend of the current light-emitting diode technology. However, since the sapphire substrate will partially absorb the luminescence of the element, the reflectivity of the element to the luminescence of the element is extremely low. For example, the reflectivity of blue light is only about 2% ~ 7%. Therefore, the light output intensity of the gallium nitride-based light-emitting element depends entirely on the light-emitting characteristics of the diode itself, and it is not possible to effectively utilize the light emitted by the diode to increase the light output intensity of the element. [Summary of the Invention] One of the objectives of this issue is to provide a method and structure for manufacturing a GaN-based light emitting diode, which can not only improve the current dispersion in the device, but also improve the light emitting diode. The light output efficiency is more effective by utilizing the light emission of 70 pieces, and the intensity of light output is greatly enhanced, thereby improving the quality and brightness of the device. In addition, another object of the present invention is to reduce the amount of static electricity accumulated in the element, effectively avoid the problem of electrostatic discharge, and reduce the damage caused by static electricity to the element. According to the above object of the present invention, a manufacturing method and structure of a gallium nitride based light emitting diode are proposed. The method according to the present invention is to first and / or a gallium nitride-based light-emitting element on the substrate. Among them, in the gallium nitride-based light-emitting element ... the first electrical gallium nitride-based semiconductor layer, the light-emitting active layer, and the second 1231055 An electrical gallium nitride-based semiconductor layer, a transparent conductive layer, a first electrical electrode and a second electrical electrode, and the substrate is, for example, a sapphire substrate to obtain a crystal and a good-quality gallium nitride-based semiconductor layer. Next, attaching—the temporary carrier on the gallium nitride-based light-emitting element 'and the “between the temporary carrier and the gallium nitride-based light-emitting element” includes—the adhesive layer used to join the temporary carrier and the gallium nitride-based light-emitting element, and then 'Remove the substrate' to fully expose the first electrical gallium nitride-based semiconductor layer of the gallium nitride-based light emitting device. Next, a reflective layer and a metal substrate layer are sequentially formed on the first electrical gallium nitride-based semiconductor layer. Finally, the temporary carrier and the adhesive layer are removed at the same time to complete the nitriding of the metal conductive substrate. Gallium based light emitting diode. Among them, the gallium nitride-based light-emitting element can be, for example, a gallium nitride (GaN) diode, and the reflective layer is made of a metal material having high reflection characteristics for blue-violet-green light, such as silver (Ag) or aluminum (A1), A part of the GaN-based diode can be reflected to increase the light output intensity of the GaN-based device. In addition, the metal substrate layer is a metal material with good conductive properties, such as silver or copper (Cu), which can provide a current distribution path for the current in the element, which improves the effectiveness of current dispersion, reduces the phenomenon of current crowding, and reduces The operating resistance of the element further increases the light output efficiency of the element. At the same time, 'for some of the accumulated static electricity generated in the device during the process', it can be conducted and released through a metal substrate layer with conductive properties' to effectively avoid the problem of electrostatic discharge. In addition, usually conductive metal substrates also have good thermal conductivity. Therefore, it helps to increase the heat dissipation of the element 'and provides excellent heat dissipation effect during the operation of the light-emitting element to maintain the operation efficiency of the element. 1231055 Therefore, in addition to the method of manufacturing the gallium nitride-based light emitting diode using the present invention, in addition to using a reflective layer to effectively utilize the light emission inside the device, the light output intensity of the device is greatly improved. The substrate is replaced with a metal substrate with good conductivity, and the current dispersion effect in the device is improved to reduce the operating resistance of the 7G device, and further improve the light output efficiency of the device. In addition, the problem of electrostatic discharge damage due to the accumulation of static electricity in the element can also be effectively avoided by using a conductive metal substrate. Therefore, the gallium nitride-based light-emitting diode manufactured by the method of the present invention not only greatly increases the brightness of the device due to the increase in light output intensity and light output efficiency, but also reduces the damage caused by the electrostatic discharge of the device. Probability, which increases the yield and reliability of GaN-based light-emitting device production. [Embodiment] The present invention provides a method and structure for manufacturing a GaN-based light-emitting diode, and a GaN-based light-emitting diode fabricated on a sapphire substrate will be transferred to a substrate by a technology of transferring a substrate. , Transfer to a metal substrate, and use the conductivity of the metal substrate to provide a good electrical conduction of the component, thereby improving the current dispersion effect in the component, and reducing the amount of static electricity in the component. At the same time, a reflective layer is provided between the metal substrate and the gallium nitride-based light-emitting diode. The reflective layer has a high reflection characteristic for light, so that the light-emitting diode can be effectively reflected into light. Another source of output, thereby increasing the light output intensity of the device. The method of the present invention will be described in detail in the following examples. 1231055 This invention discloses a method and structure for manufacturing a gallium nitride (GaN) light emitting diode. Figures 1A to 1E are sequentially referred to, and Figures 1A to 1E are schematic cross-sectional views showing the flow of a method for manufacturing a gallium nitride light emitting diode according to a preferred embodiment of the present invention. In FIG. 1A, a hafnium nitride diode device U0 having a substrate 100 is first produced. The substrate 100 is made of sapphire, for example, to obtain a gallium nitride semiconductor layer with good crystal quality, and The fabrication of a gallium nitride diode device 110 firstly sequentially forms an n-type nitride semiconductor layer 102, a light-emitting active layer 104 having a multilayer quantum well (Multi_Quantum WeU) structure, and a p-type gallium nitride. The semiconductor layer ιo6 is on the substrate 100. Next, a transparent conductive layer 108 is formed on the p-type gallium nitride semiconductor layer 106 to provide a current spreading effect. The material of the transparent conductive layer 108 may be, for example, indium tin oxide. (Indium-Tin Oxide; ITO) or Indium-Zinc Oxide (IZ0). Then, the anode electrode 112 and the cathode electrode 4 are formed on a part of the surface of the transparent conductive layer 108 and the n-type gallium nitride semiconductor layer ι02, respectively. Next, referring to FIG. 1B, using an adhesive layer 116, the gallium nitride diode element 丨 i ○ fabricated on the substrate 1000 is firstly attached to a temporary carrier 120 in the entire structure. Among them, the adhesive layer 116 can be, for example, epoxy or instant adhesive. Then, the substrate 100 is removed to expose the complete n-type gallium nitride semiconductor layer 102, as shown in FIG. 1C, and the method for removing the substrate 100 may be, for example, laser peeling 1231055 (laser lift-off) or grinding technology. Referring to FIG. 1D, after the substrate 100 is removed, a reflective layer 130 and a metal substrate layer 140 are sequentially formed in a bonding manner! ! Type gallium nitride semiconductor layer, among which the reflective layer 130 is made of a metal material with high reflectance for the emission in the wavelength range of purple, blue and green light, such as silver (Ag), aluminum (A1), nickel (Ni ), The reflectivity of (Pd) or molybdenum (Mo), especially silver or Cui Lu, is about 85% to 90%. The metal substrate layer 140 is made of a highly conductive metal material, such as silver or copper (Cu), and the thickness of the metal substrate layer 140 is significantly larger than the thickness of the reflective layer 130, so as to provide support for gallium nitride light-emitting diodes. Conductive substrate of a polar body. Finally, the adhesive layer 116 is removed to separate the temporary carrier 120 at the same time, and a gallium nitride diode device 150 having a metal substrate layer 140 is formed, as shown in FIG. 1E. The gallium nitride diode device i50 uses a metal substrate layer 140 having good conductivity as a carrier substrate. In FIG. 1E, due to the high reflection characteristics of the reflective layer 130, in addition to a portion of the light emitted directly upward, the other portion of the light emitted toward the metal substrate layer 140 is emitted by The reflection effect of the reflective layer 130 provides a light source that outputs upward, so that the light emission in the element can be effectively reused to increase the light output intensity that the element can achieve. In addition, due to the good conductive properties provided by the metal substrate layer 140, the current transfer in the element can be dispersed from the position of the anode electrode 12 to the metal substrate layer 14 and then to The position of the cathode electrode 114 is transmitted. In this way, the effect of resistance parallel connection to reduce the resistance value can be formed, and it is improved 1231055. When the cathode electrode H2 and the anode electrode 114 are made on the same plane, it is easy to generate near the n-type gallium nitride semiconductor 1G2 Current Crowding phenomenon, therefore, the operating resistance of the device is effectively reduced, thereby improving the light output efficiency of the device. In addition, for some of the accumulated static electricity generated in the device during the process, the metal substrate layer 14 with conductive properties can be used to release electricity to prevent electrostatic discharge CElectro-S ^ Dis · ㈣ESD) problem, which reduces the chance of component damage. In addition, since the metal material selected for the reflective layer Π0 also has conductive properties, it can also be used when the gallium nitride diode structure is manufactured (as shown in the figure) without first fabricating the cathode electrode 114, and the substrate transfer is completed. After that, a part of the n-type gallium nitride semiconductor layer 1G2 is removed, and then the cathode electrode ι 4 is fabricated on the reflective layer 130 to complete the current transmission situation in another light emitting diode junction m as shown in FIG. 2. , Which is represented by the current transfer path 220. > Therefore, it is possible to prevent the current crowding phenomenon from occurring at the position of the n-type gasified material conductor | 1 () 2, or the cathode electrode U4 can also be made directly below the metal substrate layer 14 to form The current distribution of the vertical current greatly improves the effectiveness of current dispersion. According to the above embodiments of the present invention, it can be known that the application of the method for manufacturing a gallium nitride light emitting diode of the present invention can not use the technology of element substrate transfer to affect the original insulating substrate without affecting the manufacturing conditions of general components. Convert to a metal substrate with good conductivity to improve the efficiency of current transfer and dispersion in the device and reduce the harm of electrostatic discharge, thereby improving the light output efficiency of the gallium nitride device and the product yield of the device manufacturing. In addition, usually 12 1231055 conductive metal substrate also has good thermal conductivity. Therefore, it helps to increase the heat dissipation of the element, and provides excellent heat dissipation effect during the operation of the light-emitting element to maintain the operating efficiency of the element. The invention also uses a reflective layer, which has a high reflection ability for the light emission of the gallium nitride element, so that the light emission in the element can be effectively used, and the part that was originally not directly output to the outside is emitted through the reflection effect of the reflective layer. And the conversion becomes a part of the actual output light source of the element, so the light output intensity of the gallium nitride element is greatly increased, thereby improving the brightness of the element. The present invention is not limited to the technology used in gallium nitride light-emitting diodes, but also all other gallium nitride-based light-emitting diode devices, such as gallium gallium nitride (InGaN) light-emitting diodes or aluminum gallium nitride. (A1GaN) ultraviolet light-emitting diodes can also be produced by the method of the present invention, which greatly improves the characteristics of the product. Although the present invention has been disclosed as above with examples, it is not intended to limit the present invention. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. The scope of protection shall be determined by the scope of the attached patent application. [Brief description of the drawings] In order to make the above features of the present invention, the purpose and advantages of the sign method more obvious and easier, with the attached drawings, it will be described as follows: Figures 1A to 1E are in accordance with the present invention. A schematic flow cross-sectional view of a method for manufacturing a gallium light-emitting diode and a method of gasification from the seed surface is preferred. Figure 2 is a schematic diagram of the structure of another photodiode according to the present invention. [Simple description of element representative symbols] 100: substrate 102, 106: gallium nitride semiconductor layer 104 · active layer 108: transparent conductive layer 110, 150 · diode element 11 2, 114: electrode 11 6: adhesive layer 120: carrier 130: reflective layer 140