1359513 九、發明說明： 【發明所屬之技術領域】 本發明係有關於氮化物多重量子井發光二極體，特別係 有關於一種具有載子提供層之氮化物多重量子井發光二極 體，藉以提供額外之載子，以及避免/降低發光層内雜質的 使用。 【先前技術】 為提高氮化鎵（GaN)系發光二極體（LED)之亮度，美國 專利第5,578,839號揭示了一種發光層（或稱主動層）摻雜有 η型雜質（例如Si)和/或p型雜質（例如Mg或Zn等）的 InxGa^N (0<χ<1)化合物半導體所製成的LED結構。此LED 結構之發光層，係夹在η型GaN系化合物半導體製成之第一 包覆層（clad layer )與ρ型GaN系化合物半導體製成之第二 包覆層中間。該LED結構在亮度上之提升，係由於上述發光 層内所摻雜之雜質提高了載子（亦即，電子和電洞）的密度， 因此有更多載子參與重新結合（recombination )所致。 相形之下，使用多重量子井（multi quantum-well, MQW) 技術之高亮度LED，通常在其發光層内係採未加摻雜之井層 (well layer)。一般MQW LED之發光層係包含有多重井層， 井層之厚度係小於半導體材料中載子的德布洛依（deBroglie ) 波長，致使電子和電洞被局限在井層内，而可達成更佳的重 新結合效率。井層通常係未加摻雜，因為井層内之雜質會導 5 1359513 摻雜有 Si 或 Ge 之 AlpInqGai.p-qN (p,q20, OSp+qSl)化合物半導 體所製成，但係具有不同之組成，且位障層需具有高於井層 之能帶隙（bandgap )。另外，載子提供層之電子濃度係為 lxlO17〜5xl02丨/cm3。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nitride multiple quantum well light-emitting diode, and more particularly to a nitride multiple quantum well light-emitting diode having a carrier-providing layer. Provide additional carriers and avoid/reduce the use of impurities in the luminescent layer. [Prior Art] In order to improve the brightness of a gallium nitride (GaN) light-emitting diode (LED), a light-emitting layer (or active layer) is doped with an n-type impurity (for example, Si) and a light-emitting layer (or an active layer) is disclosed in US Pat. No. 5,578,839. An LED structure made of an InxGa^N (0<χ<1) compound semiconductor of a p-type impurity (e.g., Mg or Zn). The light-emitting layer of the LED structure is sandwiched between a first cladding layer made of an n-type GaN-based compound semiconductor and a second cladding layer made of a p-type GaN-based compound semiconductor. The increase in brightness of the LED structure is due to the fact that the impurities doped in the above-mentioned light-emitting layer increase the density of carriers (ie, electrons and holes), so that more carriers participate in recombination. . In contrast, high-brightness LEDs using multi-quantum-well (MQ) technology typically employ an undoped well layer in their luminescent layer. Generally, the illuminating layer of the MQW LED includes multiple well layers. The thickness of the well layer is smaller than the deBroglie wavelength of the carrier in the semiconductor material, so that the electrons and holes are confined in the well layer, and the Good recombination efficiency. The well layer is usually undoped because the impurities in the well layer are made of 5 1359513 AlpInqGai.p-qN (p, q20, OSp+qSl) compound semiconductor doped with Si or Ge, but the difference is different. The composition, and the barrier layer needs to have a bandgap higher than the well layer. Further, the electron concentration of the carrier supply layer is lxlO17 to 5xl02 丨/cm3.
載子提供層的設置具有多項優點。首先，額外之電子會 被提供進MQW發光層内以與電洞重新結合，而使本發明之 LED結構達成較高的内部量子效率（internal quantum efficiency )與較高亮度。此外，由於電子之移動性（mobility ) 係大於電洞，載子提供層之設置可使電子減速，以致電子有 較高的機會與電洞重新結合，因而可達成較高之重新結合效 率。再者，攙雜進載子提供層内之Si或Ge可在不摻雜發光 層的情形下有效地使本發明之LED結構的操作電壓降低，而 又可以使發光層有更好之結晶。The provision of the carrier providing layer has several advantages. First, additional electrons are provided into the MQW luminescent layer to recombine with the holes, allowing the LED structure of the present invention to achieve higher internal quantum efficiency and higher brightness. In addition, since the mobility of the electrons is larger than that of the holes, the arrangement of the carrier supply layer can decelerate the electrons, so that the electrons have a higher chance of recombining with the holes, thereby achieving a higher recombination efficiency. Further, Si or Ge in the doping-providing layer can effectively lower the operating voltage of the LED structure of the present invention without doping the light-emitting layer, and can further crystallize the light-emitting layer.
本發明之另一特徵，是在載子提供層與發光層中間之設 置一電洞阻隔層（hole blocking layer)。此電洞阻隔層係由未 摻雜或有Si摻雜的GaN系材料製成，其具有大於發光層之能 帶隙以避免電洞逃逸進載子提供層内、並在該處與電子重新 結合。電洞阻隔層具有5 A〜0·5μηι之厚度。 電洞阻隔層之設置還具有一些額外之優點。舉例而言， 實驗證明電洞阻隔層之存在會使崩潰電壓（breakdown voltage )增加，並使本發明之LED結構的漏·;复電流（leakage 7 1359513 current )降低。此外，由於載子提供層成長後之表面上會有 一些V形的瑕疵形成，電洞阻隔層可彌補這些瑕疵使後續成 長之發光層達成較佳之結晶。在本發明之某些實施例中，電 洞阻隔層係由In掺雜或In/Si共同摻雜之GaN系材料所製 ' 成，以達成更佳之平滑化效果。其原因在於當加入銦原子時， - 可大幅提昇載子提供層之表面平滑性，進而有效地避免發光 層之瑕庇和堆疊層錯（stacking faults)。 ^ 兹配合所附圖示、實施例之詳細說明及申請專利範圍， 將上述及本發明之其他目的與優點詳述於後。然而，當可了 解所附圖示純係為解說本發明之精神而設，不當視為本發明 範疇之定義。有關本發明範疇之定義，請參照所附之申請專 利範圍。 【實施方式】Another feature of the present invention is to provide a hole blocking layer between the carrier supply layer and the light-emitting layer. The hole barrier layer is made of an undoped or Si-doped GaN-based material having a band gap larger than that of the light-emitting layer to prevent holes from escaping into the carrier-providing layer and where the electrons are re-established. Combine. The hole barrier layer has a thickness of 5 A to 0.5 μm. The arrangement of the hole barrier layer also has some additional advantages. For example, experiments have shown that the presence of a hole barrier layer increases the breakdown voltage and reduces the leakage current of the LED structure of the present invention (leakage 7 1359513 current). In addition, since the V-shaped ruthenium is formed on the surface of the carrier-providing layer, the hole-blocking layer can compensate for these 瑕疵 to achieve better crystallization of the subsequently grown luminescent layer. In some embodiments of the invention, the hole barrier layer is made of a GaN-based material that is doped with In or Si to achieve a better smoothing effect. The reason is that when the indium atom is added, the surface smoothness of the carrier-providing layer can be greatly improved, thereby effectively avoiding the opaque layer and the stacking faults. The above and other objects and advantages of the present invention will be described in detail with reference to the accompanying drawings. However, it is to be understood that the appended drawings are merely illustrative of the scope of the invention. For the definition of the scope of the invention, please refer to the attached patent application. [Embodiment]
• 第1圖所示係依據本發明之第一實施例的氮化物MQW LED結構之示意圖。請注意到本說明書係使用「LED結構」 一詞來指稱一個LED之磊晶結構，另外以「LED裝置」一詞 來指稱一個LED.結構形成之後，再經過後續的晶片程序（chip process)在LED結構上形成電極後所得之半導體裝置。• Fig. 1 is a schematic view showing the structure of a nitride MQW LED according to a first embodiment of the present invention. Please note that this manual uses the term "LED structure" to refer to the epitaxial structure of an LED. In addition, the term "LED device" is used to refer to an LED. After the structure is formed, it passes through a subsequent chip process. A semiconductor device obtained by forming an electrode on an LED structure.
如第1圖所示，在上述LED結構之底部，一基板10通 常係以氧化鋁單晶（藍寶石）或是具有與LED結構之磊晶層 接近的晶格常數之氧化物單晶製成。該基板10亦可由SiC 8 1359513 之AlpInqGa|_p_qN(p^〇，(^p+q引）化合物半導體製成而具有 在lxl〇17/Cm3與5xl〇2i/cm3之間的電子濃度。這些井層41和 位障層42係具有獨立之组成，但位障層42具有較井層μ為 高之能帶隙（Eg)。井層4丨和位障層42均係在6〇〇t與丨2〇〇它 之間的成長溫度下形成，但位障層42有較高之成長溫度。 接著’在載子提供層40的上表面，形成本實施例之 發光層50〇MQW發光層5〇係由多數之井層5i和多數之位 障層52交替堆疊形成。井層51和位障層52均係由未加摻雜 之AlxIn>’Ga丨-^^^^，。(^分+^”化合物半導體製成但各具 有獨立之組成，該位障層52具有較井層51者為高之能帶隙 (Eg)。這些井層51和位障層52亦係在^(^與12〇〇t之間 的不同成長溫度下形成，但位障層52有較高之成長溫度。載 子提供層40之井層41，係具有適當之AlpInqGai "N(p，杧〇, 〇SP+qSl)組成，而使其能帶隙大於發光層5〇之井層5丨的 AlxIriyGa^yN (x，y2〇,〇sx+yS1)。請注意到，本實施例之發光 層50結構僅屬例示，本發明之精神並不限定發光層5〇需要 一個特定之MQW結構。 載子提供層40之作用在提供額外電子進入MqW發光層 5〇内，以便與電洞重新結合，而使本發明之LED結構達成較 向之内部量子效率並進而達成較高亮度。此外，由於電子之 移動性已知係大於電洞，載子提供層4〇之設置亦可使電子減 10 速，使其有較高的機會與電洞重新結合，因而可達成較高之 重新結合效率。更進一步的是，攙雜進載子提供層40内之 Si或Ge可使本發明之LED結構，在不摻雜發光層50的情形 下同樣能有效地降低操作電壓，此外，載子提供層40復可促 使後續成長之發光層50具有更好之結晶。 最後，在發光層50之上表面，以和第一導電型相反的第 二導電型GaN系材料形成第二接觸層60。因此，在本實施例 中，第二接觸層60係以一種p型GaN系材料製成（以相對 於第一接觸層30的η型GaN系材料）。在某些其他實施例中， 第二接觸層60亦可以η型GaN系材料製成。設置第二接觸 層60之目的係為了在後續的晶片程序中，提供後續形成之p 型電極所需的歐姆接觸。 第2圖所示係依據本發明之第二實施例的氮化物MQW LED結構之示意圖。基本上，本實施例在結構上係與第一實 施例相類似，唯一不同處係在於載子提供層40與發光層50 之間設置有一層電洞阻隔層70。提供電洞阻隔層70之兩個 最重要的理由是：（1)避免發光層50之電洞逃逸至載子提供 層40並在該處與電子以非發光方式重新結合；以及（2)在載子 提供層40成長之後，使其表面上所形成之V形瑕疵平滑化， 而使後續成長之發光層50可以達成較佳之結晶。 電洞阻隔層70係在600°C與1200°C之間的成長溫度下， 未加擦雜、或有Si掺雜、或有In摻雜、或有In/Si共同摻 A雜之⑽_ ’形成在載子提供層40之上表面，而具有5 〜之間的厚度。電洞阻隔層心材料在係具有大於發 "層50之月⑽隙’以避免電洞逃逸進入載子提供層4〇内。 有& t雜之目的是進—步提昇載子提供層4G之表面平滑 性，以有效地避免發光層5〇之瑕疲和堆疊層錯。根據實驗證 明’電洞阻隔層7〇之在力夹 之存在尚具有其他額外之優點，諸如使本 發明之咖結構的崩潰„(Vb)增加’以及使其㈣ 降低。 傳統上’第1和2圖中所顯示之LED結構，接著需經過 一晶片程序以形成LED對外電氣連結的電極、以及製備該 咖以利封裝。第3圖所示係第i圖之LED結構在經過該晶 片程序後的LED裝置之示意圖。請注意到是相同之晶片程 序同樣可應用至第2圖中所顯示之咖結構，但為簡化起 見，下文係以第I圖之LED結構作為範例。 首先’ LED結構被適當地加以钱刻，藉以暴露出第一接 觸層3〇之一部份上表面。接著，在第一接觸層30被暴露區 域的上表面’以適當之金屬材料形成第一電極91。另一方面， 在第二接觸層60之上表面，形成—透明導電層㈤卿咖 conductive layer) 8〇。此透明導電層8()可為—金屬導電層 (metallic conductive laye〇或透明氧化物層（㈣啊咖 12 1359513As shown in Fig. 1, at the bottom of the LED structure, a substrate 10 is usually made of an oxide single crystal (sapphire) or an oxide single crystal having a lattice constant close to the epitaxial layer of the LED structure. The substrate 10 can also be made of AlpInqGa|_p_qN (p^〇, (^p+q)) compound semiconductor of SiC 8 1359513 with an electron concentration between lxl〇17/Cm3 and 5xl〇2i/cm3. The layer 41 and the barrier layer 42 have an independent composition, but the barrier layer 42 has an energy band gap (Eg) higher than the well layer μ. The well layer 4 and the barrier layer 42 are both at 6 〇〇t and丨2〇〇 is formed at a growth temperature between them, but the barrier layer 42 has a higher growth temperature. Next, 'on the upper surface of the carrier supply layer 40, the light-emitting layer 50〇MQW of the present embodiment is formed. The lanthanide system is formed by alternately stacking a plurality of well layers 5i and a plurality of barrier layers 52. The well layer 51 and the barrier layer 52 are both undoped AlxIn>'Ga丨-^^^^, (^ +^" compound semiconductors, but each having an independent composition, the barrier layer 52 has a higher energy band gap (Eg) than the well layer 51. These well layers 51 and the barrier layer 52 are also attached to ^(^ Formed at different growth temperatures between 12 〇〇t, but the barrier layer 52 has a higher growth temperature. The carrier layer 41 of the layer 40 is provided with the appropriate AlpInqGai "N(p, 杧〇, 〇SP+qSl) And the band gap is larger than the well layer 5 丨 of the light-emitting layer 5 丨 AlxIriyGa^yN (x, y2 〇, 〇 sx + yS1). Please note that the structure of the luminescent layer 50 of the present embodiment is merely an example, The spirit of the invention does not limit the need for a particular MQW structure for the luminescent layer 5. The carrier providing layer 40 functions to provide additional electrons into the MqW luminescent layer 5 to recombine with the holes, thereby enabling the LED structure of the present invention. Achieve a higher internal quantum efficiency and thus achieve higher brightness. In addition, since the mobility of electrons is known to be larger than the hole, the arrangement of the carrier providing layer 4 can also reduce the electron speed by 10, making it higher. The opportunity is recombined with the hole, so that a higher recombination efficiency can be achieved. Further, the Si or Ge in the doping carrier 40 can make the LED structure of the present invention undoped with the luminescent layer 50. In this case as well, the operating voltage can be effectively reduced. In addition, the carrier supply layer 40 can promote the subsequent growth of the luminescent layer 50 to have better crystallization. Finally, on the upper surface of the luminescent layer 50, opposite to the first conductivity type. Second conductivity type GaN-based material formation The second contact layer 60. Therefore, in the present embodiment, the second contact layer 60 is made of a p-type GaN-based material (in an n-type GaN-based material with respect to the first contact layer 30). In some other implementations For example, the second contact layer 60 can also be made of an n-type GaN-based material. The second contact layer 60 is provided for the purpose of providing an ohmic contact required for a subsequently formed p-type electrode in a subsequent wafer process. The figure shows a schematic diagram of a nitride MQW LED structure in accordance with a second embodiment of the present invention. Basically, the present embodiment is similar in structure to the first embodiment, and the only difference is that a hole blocking layer 70 is provided between the carrier supply layer 40 and the light-emitting layer 50. The two most important reasons for providing the hole barrier layer 70 are: (1) avoiding holes in the luminescent layer 50 from escaping to the carrier providing layer 40 where they are recombined with electrons in a non-luminescent manner; and (2) After the carrier supply layer 40 is grown, the V-shaped yt formed on the surface thereof is smoothed, so that the subsequently grown luminescent layer 50 can achieve better crystallization. The hole barrier layer 70 is at a growth temperature between 600 ° C and 1200 ° C, without rubbing, or with Si doping, or with In doping, or with In / Si co-doping (10)_ ' It is formed on the upper surface of the carrier supply layer 40 and has a thickness of between 5 and 〜. The hole barrier core material has a month (10) gap greater than that of the layer 50 to prevent holes from escaping into the carrier supply layer 4 . The purpose of & t miscellaneous is to further enhance the surface smoothness of the carrier providing layer 4G to effectively avoid the fatigue of the luminescent layer 5 and the stacking fault. According to experiments, it has been proved that the presence of the hole barrier layer 7 has other additional advantages, such as increasing the collapse of the coffee structure of the present invention (Vb) and reducing (4). Traditionally, '1st and 2 The LED structure shown in the figure is then subjected to a wafer process to form an electrode for externally electrically connecting the LED, and to prepare the package for encapsulation. Figure 3 is an LED structure of the first embodiment after passing through the wafer program. Schematic diagram of the LED device. Please note that the same wafer program can be applied to the coffee structure shown in Fig. 2, but for the sake of simplicity, the LED structure of Fig. 1 is taken as an example. Firstly, the LED structure It is appropriately engraved to expose the upper surface of a portion of the first contact layer 3. Then, the first electrode 91 is formed of a suitable metal material on the upper surface of the exposed portion of the first contact layer 30. In one aspect, a transparent conductive layer (8) is formed on the upper surface of the second contact layer 60. The transparent conductive layer 8 can be a metallic conductive layer or a transparent oxide layer. ((4) ah coffee 12 1359513
oxide layer)。該金屬導電層係由下列材料、但不僅限於這些 材料所製成：Ni/Au合金、Ni/Pt合金、Ni/Pd合金、Pd/Au合 金、Pt/Au 合金、Cr/Au 合金、Ni/Au/Be 合金、Ni/Cr/Au 合金、 Ni/Pt/Au合金、和Ni/Pd/Au合金。另一方面，透明氧化物層 係由下列材料、但不僅限於這些材料所製成：ITO、CTO、 ZnO:Al、ZnGa2〇4、Sn〇2:Sb、Ga2〇3:Sn、AgIn02:Sn、In2〇3:Zn、 CuA1〇2、LaCuOS、NiO ' CuGa〇2、和 SrCu2〇2 0 接下來，在 透明導電層80之上表面、或如第3圖所示的在透明性導電層 80之側邊，形成第二電極92。第二電極92係由下列材料' 但不僅限於這些材料所製成：Ni/Au合金、Ni/Pt合金、Ni/Pd 合金、Ni/Co合金、Pd/Au合金、Pt/Au合金、Ti/Au合金、 Cr/Au 合金、Sn/Au 合金、Ta/Au 合金、TiN、TiWNx (泛0)、 和 WSiy (於〇) 0Oxide layer). The metal conductive layer is made of, but not limited to, the following materials: Ni/Au alloy, Ni/Pt alloy, Ni/Pd alloy, Pd/Au alloy, Pt/Au alloy, Cr/Au alloy, Ni/ Au/Be alloy, Ni/Cr/Au alloy, Ni/Pt/Au alloy, and Ni/Pd/Au alloy. On the other hand, the transparent oxide layer is made of, but not limited to, the following materials: ITO, CTO, ZnO: Al, ZnGa2〇4, Sn〇2: Sb, Ga2〇3: Sn, AgIn02: Sn, In2〇3: Zn, CuA1〇2, LaCuOS, NiO'CuGa〇2, and SrCu2〇2 0 Next, on the upper surface of the transparent conductive layer 80, or in the transparent conductive layer 80 as shown in FIG. On the side, a second electrode 92 is formed. The second electrode 92 is made of the following materials 'but not limited to these materials: Ni/Au alloy, Ni/Pt alloy, Ni/Pd alloy, Ni/Co alloy, Pd/Au alloy, Pt/Au alloy, Ti/ Au alloy, Cr/Au alloy, Sn/Au alloy, Ta/Au alloy, TiN, TiWNx (pan 0), and WSiy (in 〇) 0
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 也例來對本創作之範脅加以限制。相反地，其目的是希望能 函孤各種改變及具相等性的安排於本創作所欲申請之專利範 圍的範嘴内。 【圖式簡單說明】 圖所示係依據本發明之第一實施例的氮化物 結構之示意圖。 13 1359513 第2圖所示係依據本發明之第二實施例的氮化物MQW LED 結構之示意圖。 第3圖所示係第1圖之LED結構在經過晶片程序後的LED 裝置之示意圖。 【主要元件符號說明】 10 基板 20 緩衝層 30 第一接觸層 40 載子提供層 41 井層 42 位障層 50 發光層 51 井層 52 位障層 60 第二接觸層 70 電洞阻隔層 80 透明導電層 91 第一電極 92 第二電極 14The features and spirit of the present invention are more clearly described in the above detailed description of the preferred embodiments, and are not intended to limit the scope of the present invention. On the contrary, the purpose is to hope that the various changes and equal arrangements can be arranged in the scope of the patent scope of the application. BRIEF DESCRIPTION OF THE DRAWINGS The figure shows a schematic view of a nitride structure according to a first embodiment of the present invention. 13 1359513 Figure 2 is a schematic illustration of a nitride MQW LED structure in accordance with a second embodiment of the present invention. Figure 3 is a schematic diagram of the LED device of Figure 1 after passing through the wafer process. [Main component symbol description] 10 substrate 20 buffer layer 30 first contact layer 40 carrier supply layer 41 well layer 42 barrier layer 50 light-emitting layer 51 well layer 52 barrier layer 60 second contact layer 70 hole barrier layer 80 transparent Conductive layer 91 first electrode 92 second electrode 14