1236773 玖、發明說明： 【發明所屬之技術領域】 本發明疋有關於一種發光元件（light—emitung device)，特別是指一種高效率發光元件。 5 【先前技術】 由於發光二極體（light - emitting diode;簡稱 LED) 具有體積小之優勢，因此已被廣泛應用於顯示器背光模 組、通訊、電腦、交通號誌及玩具等消費市場。 為了解決有關發光二極體亮度不夠的問題，科學家們 10 從數個方面來提高元件的亮度。例如：在磊晶技術 (epitaxial technology)方面主要盡量提昇施體（d〇nor) 及受體（acceptor)的濃度，並設法減低發光層（active layer)的差排密度（dislocation density)。由於提高發 光層中的受體濃度並不容易，特別是在寬能隙氮化鎵（簡 15 稱GaN)糸統有其難度。同時由於藍寶石（sapphire)基板與 鼠化鍊材料存在相當大的晶格不匹配（lattice mismatch)，因此設法減低發光層中的差排密度之技術並 不容易突破。 此外，熟知LED相關領域的技術者皆知，由於構成藍 20 光LED之藍寶石基板、半導體（GaN)磊晶層及透光性接觸 電極（contact electrode)層是呈相互平行的設置關係， 且GaN折射率（ref ractive index)大，因此，可藉甴以折 射率小的藍寶石基板與透光性接觸電極層夾著折射率大 的GaN蠢晶層以形成波導（waveguide)路徑。但熟知光學 1236773 領域者皆知，一入射（incident)光源可構成反射 (inflection)的條件在於，該入射光源的入射角需大於一 特疋臨界角。雖然可藉由使該入射光源的入射角以大於該 特定臨界角的角度，入射該藍寶石基板或透明接觸電極層 5 的界面，以重複地全反射該入射光源並傳播至波導路徑 内。但，在具有疊層構造的GaN磊晶層内橫向地傳播，亦 會產生光源被吸收及衰減等問題而影響LED整體的外部量 子效率（external quantum efficiency) ° 參閱圖1，一種半導體發光元件（中華民國專利公告案 1〇 號為561632)’包含：一藍寶石基板10、一形成在該藍寶 石基板10上的N型半導體層11、一形成在該n型半導體 層11並可產生一預定波長範圍的光源的發光層12 ,及一 形成在該發光層12上的P型半導體層13。 該藍寶石基板10的一上表面形成有複數重複地排列 15 的凹部14。其中，該藍寶石基板10是使用C面（00 01)的 藍寶石基板，且構成該等凹部14的邊是大致平行於該N 型半導體層11的成長穩定面（stabilized growth surface，此處所k及的成長穩定面為Μ面；意即彳1^00卜 面）’以使形成在該藍寶石基板10上的N型半導體層11 20 不產生結晶缺陷（crystal defect)。每一凹部14的深度 及尺寸分別是1 μπι及10 μιη，並藉由每一凹部14的一中 心界定出一 1 〇 μιη的間距。 在此以该藍寶石基板10上是形成複數凸部1 〇 2，說明 該Ν型半導體層11成長於該藍寶石基板1〇的磊晶演變過 1236773 程。參閱圖2,該藍寶石基板10具有一基面1〇1及複數由 該基面101凸伸而出的凸部102(圖2中僅以一凸部1〇2顯 示）。當該N型半導體層η在該藍寶石基板1〇上成長時， 5亥Ν型半導體層11是自該基面101及該凸部1〇2頂面成 長’而位於該凸部1 〇2之周面處的成長速度則較為遲緩。 參閱圖3，當自該基面101及該凸部1〇2頂面成長的該Ν 型半導體層11交會時，則交會處的該Ν型半導體層之 成長速度加快。最後，平坦地形成結晶性（crystalliriity) 佳且不具空洞的該N型半導體層11。 在參閱圖1 ’設置在該藍寶石基板上的複數凹部 14的設計，對於該半導體發光元件有下列功效：首先，藉 由該等凹部14造成該光源的散射（scattering)或繞射 (diffraction) ’並減少因橫向傳播造成的損失及吸收且 增加該半導體發光元件的外部量子效率。此外，由於該藍 寶石基板10及該N型半導體層11之間不產生結晶缺陷， 可增加内部量子效率（internal quantum efficiency)。 再者，由於該N型半導體層11可完全地掩埋該等凹部14, 以避免不需要的封閉孔造成該光源散射或繞射時的阻礙。 但是，熟知材料晶體學（crystallography)領域者皆 知’在不同晶格常數（lattice constant)的界面處，皆會 產生晶格不匹配的現象。此外，隨著兩種不同晶格常數之 材質的接觸面積越大及累積的原子層厚度越大時，伴隨著 晶格不匹配現象而產生的差排（即所謂的線缺陷）密度也 隨之變高。由上述半導體發光元件的概念可得，該N型半 1236773 導體層11可完全地掩埋該等凹部14，意即表示該藍寶石 基板10及該N型半導體層u兩者的接觸面積大。因此， 由晶體學的理論可知，該半導體發光元件的内部量子效率 將因大量的差排密度而大幅地降低，並影響該半導體發光 5 元件的外部量子效率。 因此，如何達到發光二極體的高内部量子效率的同 時，亦可兼顧優良的外部量子效帛，是研究開發發光二極 體的相關業者所需克服的一大難題。 【發明内容】 10 發明概要 發明人是基於晶體學原理，利用降低差排密度的觀點 以提高半導體發光元件的内部量子效率。如圖4所示，在 一藍寶石基板90上形成一具有複數凹槽9〇1的預定圖案 (但在圖4中僅以一凹槽901說明之），將該等凹槽901的 15 差階（steP ;亦可稱凹槽901的深度）控制在5 μιη以下， 並將該等凹槽901的尺寸及間距分別控制在7 μιη以下。 此外’利用検向磊晶技術（lateral epitaxial growth)， 控制榼向的磊晶速度大於縱向的磊晶速度，以使得位於該 等凹槽901差階處的半導體磊晶體9〇2(epitaxial 20 (^%41)之一成長穩定面為彳112〇面族群的晶面（在圖4 中，疋以彳11 22 面族群表示之）。由此，使得該半導體磊 晶體902於成長過程中，藉由該成長穩定面（彳面族 群的晶面）可分別與該等凹槽901共同界定出複數封閉孔 (closed p〇res)903 〇 1236773 由上述之該藍寶石基板90的該等凹槽901與該半導 體磊晶體902的成長穩定面之間所界定出的該等封閉孔 903可知，發明人是藉由減少該藍寶石基板9〇與該半導體 磊晶體902之間的接觸面積以降低差排密度，並增加由該 半導體磊晶體902產生之光源的内部量子效應且同時提高 外部量子效應。此外，該等凹槽901可形成該光源的繞射 及散射，並減少因橫向傳播造成的損失。再者，由於該等 封閉孔903的尺寸小於是1 μη，因此該等封閉孔9⑽並不 會構成散熱不良的問題。 發明之詳細說明 因此，本發明之目的，即在提供一種高效率發光元件。 本發明之高效率發光元件，包含：一基板，及一形成 在該基板上的蠢晶體。 該基板具有一基面及複數相間隔地由該基板之基面 凹陷的凹槽。 該磊晶體具有一基面及複數由該磊晶體之基面凸伸 而出的凸柱。該磊晶體的凸柱是分別設置於該基板的凹槽 内。該基板的每一凹槽與該磊晶體的每一凸柱相配合界定 出複數封閉孔。 值得一提的是，雖然本發明之該高效率發光元件是藉 由該基板上的凹槽與該磊晶體上的凸柱相配合界定出該 等封閉孔，以減少該基板及該磊晶體之間的接觸面積並降 低差排密度，而達到高内部量子效率的特點。相對地，本 發明之高效率發光元件的該等封閉孔也可以是藉甴在該 1236773 基板上形成複數相間隔設置的凸柱，使得磊晶於該基板上 的蠢晶體是具有相間隔地由該磊晶體之一下表面凹陷的 凹槽’並藉由該基板上的凸柱及該磊晶體上的凹槽相配合 界定出該等封閉孔，以減少該基板及該磊晶體接觸的面積 5 並降低差排密度，而達到高内部量子效率的特點。 適用於本發明之該基板是選自於下列所構成之群 組：藍寶石（sapphire)、碳化矽（SiC)及矽（Si)。較佳地， 該基板是藍寶石（sapphire)。在一具體例中，該基板的基 面是該藍寶石的一 C面，該C面為（〇〇〇1)面。 10 較佳地，該磊晶體自該基板向遠離該基板的方向依序 具有一第一型半導體層、一局部覆蓋該第一型半導體層的 發光層及一覆蓋該發光層的第二型半導體層，該磊晶體的 凸柱是形成於該第一型半導體層。 較佳地’該磊晶體是由一含有皿族及V族元素之半導 15 體化合物所製成。值得一提的是，在使得本發明之高效率 發光元件的磊晶體產生一頻率介於700 nm至550 nm的光 源之含有El族及V族元素之半導體化合物中，該瓜族元素 是選自於下列所構成之群組··鋁（A1)、鎵（Ga)、銦（丨“及 此等之一組合；該V族元素是選自於下列所構成之群組： 20 磷（P)及砷（As)。另外，在使得本發明之高效率發光元件 的蠢晶體產生一頻率介於550 nm至370 nm的光源之含有 ΠΙ族及V族元素之半導體化合物中，該羾族元素是選自於 下列所構成之群組：鋁（A1)、鎵（Ga)、銦（In)及此等之一 組合；該V族元素是氮（N)。在一具體例中，該瓜族元素 10 1236773 及該v族元素分別是鎵（Ga)及氮⑻，即該含有瓜族及v 族元素之半導體化合物是含有氮化鎵（簡稱⑽）之半導體 化合物。 車又佳地該第一型半導體層是一 n型（n-type)半導體 層’該第二型半導體層是一 M(p_type)半導體層。 較佳地，本發明之高效率發光元件更包含有一形成在 該第-型半導體層上的第—接觸電極（eQntaet)，及―形 成在該第二型半導體層上的第二接觸電極。 . 較佳地’該蟲日日日體是-六方（hexagQnal)晶體，該蟲_ 晶體之基面是平行於該基板的基面。 較佳地，該磊晶體的一成長穩定面是選自於下列所構 成之群組的彳112Z卜面族群：（ll2z)、（l2lz)、（2llz)、 (ll2z)、（piz)及（2Hz)。在一具體例中，z等於Q。因此， 在一具體例中，該彳ll^z丨面族群為彳112〇卜面族群。該 面族群是選自於下列所構成之群組：（11彡〇)、 (1土1〇)、（2110)、（Π20)、（00)及（2^0)。 _ 較佳地，該基板上的該等凹槽是呈一陣列s(array) _ 排列。 - 較佳地，該基板之每一凹槽具有一介於〇· 5 μιη至5 μ[η 之間的預定深度。 較佳地，該基板之每一凹槽具有一介於2 111111至7 μιη 之間的預定尺寸。藉該基板之每一凹槽的一中心界定出一 介於2 μιη至7 μιη之間的預定間距。 值得一提的是，該基板上的該等凹槽是藉由一設置在 11 1236773 該基板上並具有一預定圖案的遮罩（mask)，利用微影蝕刻 法（photolithography)所形成。較佳地’該預定圖案是選 自於下列所構成之群組：陣列式排列的圓形、陣列式排列 的等四邊形、陣列式排列的等六邊形及陣列式排列的等三 邊形。在-具體例中，該預定圖案是陣列式排列的圓形。 本發明之功效在於，藉由該等封閉孔減少該基板及該 磊晶體接觸的面積以降低差排密度，並使得本發明之發光 元件達到高内部量子效率的特點。 【實施方式】 有關本發明之則述及其他技術内容、特點與功效，在 以下配合參考圖式之一具體例的詳細說明中，將可清楚的 明白。 〈具體例〉 參閱圖5，本發明之高效率發光元件的一具體例，包 含：-藍寶石基板2、-形成在該藍寶石基板2上的_ 磊晶體3、一 Ti/Al/Ti/Au接觸電極41，及一 Ni/Au接觸 電極42。 該藍寶石基板2具有一為（00 01)面的基面21，及複數 相間隔地由該基板2之基面21凹陷的凹槽22。每一凹槽 22具有一 1·5 μπι的深度、一 3 μιη的尺寸。每一凹槽22 之一中心界定出一 3 μιη的間距。 其中’在該藍寶石基板2上形成有一具有一呈陣列式 排列的圓形圖案之遮罩（圖未示）’並利用乾蝕刻（dry etching)法在該藍寶石基板2上形成該等凹槽22，以製作 12 1236773 出具有該等凹槽22之藍寶石基板2(如圖6所示）。 該GaN蠢晶體3具有一為（0001)面的基面31及複數 由該GaN磊晶體3之基面31凸伸而出的凸柱32。該GaN 猫晶體3的凸柱32是分別設置於該藍寶石基板2的凹槽 5 22内。該藍寶石基板2的每一凹槽22與該GaN蠢晶體3 的每一凸柱32相配合界定出複數封閉孔5。該GaN磊晶體 3自該GaN基板3向退離該GaN基板3的方φ，依序具有 一 η-GaN半導體層33、一局部覆蓋該n-GaN半導體層33 的發光層34及一覆蓋該發光層34的p-GaN半導體層35。 其中’該GaN蟲晶體3的凸柱32是形成於該η-GaN半導 體層33。 此處形成在該藍寶石基板2上的η-GaN半導體層33， 疋利用橫向蠢晶技術並控制該η-GaN半導體層33之橫向 的磊晶速度大於縱向的磊晶速度，以使得位於該藍寶石基 15 板2之凹槽22差階處的η-GaN半導體層33之一成長穩定 面為彳ii2(U面族群。藉該彳π2〇卜面族群，使得在該n_GaN 半導體層33的磊晶過程中是以沿著該等凹槽22之周邊呈 -三角形狀的方式覆蓋該等凹#22(此現象可見於圖7)。 由前所述並配合參閱圖5,每一凹槽22與形成在該藍 2〇 f石基板2上的n-GaN半導體層33可構成三個封閉孔5(此 現象則可見於圖8)。但’由於圖8為該具體例一之藍寶石 基板2與該n-GaN半導體層33之間的—婦描式電;顯微 鏡（scanmng eiectron micr_pe;簡稱卿截面形貌 圖，僅顯示出前述之三個封閉孔5中的兩個封閉孔5，因 13 1236773 此，該第三個封閉孔5可以是被隱藏在位於該凹槽22内 的n-GaN半導體層33的後側或前側。 該發光層34具有一連接於該n-GaN半導體層33的 n-AlGaN膜341、一連接於該p-GaN半導體層35的p-AlGaN 5 膜343,及一被夾置於該n-AlGaN膜341與p-AlGaN膜343 之間的多層量子井（multi^quantum wal 1 ;簡稱MQW)342。 該多層量子井342的結構為（InGaN/GaN)n。 該Ti/Al/Ti/Au接觸電極41及該Ni/Au接觸電極42， 是分別形成在該η-GaN半導體層33及該p-GaN半導體層 _ 1〇 34 上。 參閱圖9,為形成在該η-GaN半導體層33上之差排密 度對凹槽深度關係圖。由圖9可得，當橫座標（凹槽深度） 越大，相對地縱座標（差排密度）越小。 參閱圖10，為形成在該n-GaN半導體層33上之差排 15 密度的原子力顯微鏡（atomic force microscope;簡稱AFM)— 形貌圖。由圖10顯示出形成於該n-GaN半導體層33上的 差排為呈六邊形的貫穿式差排（threading修 dislocation)，其掃描面積為5 μιη χ 5卿，且差排密度 _ 是低於 3 X 108cnT2。 20 參閱圖H，為該具體例之發光元件及一傳統發光元件 (意即傳統的發光二極體）的電流對電壓關係比較圖。由圖 11可得，該具體例在電壓為—5V時的逆向漏電 leakage current ;簡稱Ir)遠比該傳統的發光二極體之逆 向漏電流值小，僅為〇·24 nA，其結果代表該具體例之漏 14 1236773 電流值較低。 參閱圖12,該具體例之發光元件及該傳統發光二極體 的光源輸出功率對電流關係比較圖。其結果顯示，在相同 的輸出電流值之下，該具體例之發光元件具有較高的光源 5 輸出功率，其原因在於，該具體例之發光元件的差排密度 車父低，因此由該發光層33產生的光源之内部量子效率較 高。由前所述，該具體例之高效率發光元件具有較高的内 部量子效率，因此也使得外部量子效率增加並具有較高的 光源輸出功率值。 10 參閱圖丨3,為一不同電流注入值之光致螢光光譜 (electroluminescence spectrum;簡稱 EL· 光譜）比較分 析圖。由於，造成一發光二極體之波長偏移的主因之一在 於散熱不良。然而，界於藍寶石基板及n_GaN半導體層之 間的封閉孔空間過大，則是導致散熱不良的原因之一。由 15 圖13顯示，一傳統的發光二極體與具有1.5 μιη凹槽深度 圖案之藍寶石基板的發光二極體相比較下，其波長的偏移 量幾乎相ϋ ’亦即’該具體例之發光元件内的封閉孔不影 響其元件的散熱性。 綜上觀之，本發明之高效率發光元件，具有差排密度 20 ⑻、内部篁子效率高、漏電流小、散熱佳及光源輸出功率 高等特點，確實達到本發明之目的。 惟以上所述者，僅為本發明之較佳實施例而已，當不 能以此限定本發明實施之範圍，即大凡依本發明申請專利 範圍及發明說明書内容所作之簡單的等效變化與修飾，皆 15 1236773 應仍屬本發明專利涵蓋之範圍内。 【圖式簡單說明】 件 圖JL疋一正視示意圖，說明 牛導體發光元 圖2是一正視剖面示意、圖，說明該習知之一 n型半導 體層成長於一藍寶石基板的磊晶演變過程之前段； 圖3是一正視剖面示意圖，說明該習知之該n型半導 體層成長於該藍寶石基板的磊晶演變過程之後段； ίο 15 20 圖4是一蟲晶演變示意圖，說明本發明之發明概念； 圖5是一正視示意圖，說明本發明之高效率發光^件 的一具體例； 圖6是一 SEM俯視形貌圖，說明該具體例之一藍寶石 基板上的凹槽； 圖7疋一 SEM形貌圖，說明一 n—半導體層在一磊 晶過程中與該藍寶石基板之凹槽的關係； 圖8是一SEM截面形貌圖； 圖9是一差排密度對凹槽深度關係圖； 圖10是一 AFM形貌圖； 圖11是一電流對電壓關係比較圖； 圖12是一光源輸出功率對電流關係比較圖；及 圖13是一不同電流注入對應乩峰值波長關係比較圖。 16 1236773 【圖式之主要元件代表符號簡單說明】 2......... ，·…藍寶石基板 343 …·， …"·ρ-AlGaN 膜 21……. …··基面 35……. ……p-GaN半導體層 22……· …··凹槽 41……. ……Ti/Al/Ti/Au接觸電極 3……… —*GaN 日日體 42……《 ……Ni/Au接觸電極 3卜…·. ......基面 5......... …··封閉孔 32……· …··凸柱 90……. "…藍寶石基板 33……· •…·n GaN半導體層 901 …·. …··凹槽 34……. ......發光層 902 … .....半導體减日日體 341 …·, …“η-AlGaN 膜 903 … …··封閉孔 342 …·. ••…多層量子井 171236773 发明 Description of the invention: [Technical field to which the invention belongs] The present invention relates to a light-emitung device, and particularly to a high-efficiency light-emitting device. 5 [Previous Technology] Because light-emitting diodes (LEDs for short) have the advantage of small size, they have been widely used in consumer markets such as display backlight modules, communications, computers, traffic signs, and toys. In order to solve the problem of insufficient brightness of light-emitting diodes, scientists 10 have increased the brightness of components in several ways. For example, in epitaxial technology, the concentration of donor and acceptor is mainly increased as much as possible, and the dislocation density of the active layer is reduced. Since it is not easy to increase the acceptor concentration in the light-emitting layer, especially in the wide band gap gallium nitride (GaN) system, it is difficult. At the same time, due to the considerable lattice mismatch between the sapphire substrate and the ratified chain material, it is not easy to break through the technology of reducing the differential density in the light-emitting layer. In addition, those skilled in the field of LEDs know that the sapphire substrate, semiconductor (GaN) epitaxial layer, and transparent contact electrode layer constituting the blue 20 light LED are arranged in parallel with each other, and GaN The refractive index (ref ractive index) is large. Therefore, a sapphire substrate having a small refractive index and a light-transmitting contact electrode layer may be used to form a waveguide path by sandwiching a GaN stupid layer having a large refractive index. However, it is well known to those skilled in the field of optics 1236773 that the condition that an incident light source can constitute reflection is that the incident angle of the incident light source must be greater than a special critical angle. Although the incident angle of the incident light source can be made to be at an angle larger than the specific critical angle, the interface of the sapphire substrate or the transparent contact electrode layer 5 is incident to totally reflect the incident light source repeatedly and propagate into the waveguide path. However, lateral propagation in a GaN epitaxial layer with a stacked structure also causes problems such as absorption and attenuation of the light source, which affects the overall external quantum efficiency of the LED. See FIG. 1, a semiconductor light emitting element ( Republic of China Patent Publication No. 10 is 561632) 'includes: a sapphire substrate 10, an N-type semiconductor layer 11 formed on the sapphire substrate 10, and an n-type semiconductor layer 11 formed and can generate a predetermined wavelength range A light emitting layer 12 of a light source, and a P-type semiconductor layer 13 formed on the light emitting layer 12. The upper surface of the sapphire substrate 10 is formed with a plurality of recesses 14 which are repeatedly arranged 15. The sapphire substrate 10 is a sapphire substrate using a C-plane (00 01), and the sides constituting the recesses 14 are substantially parallel to a stabilized growth surface (stabilized growth surface of the N-type semiconductor layer 11). The growth-stable surface is the M-plane; that is, 彳 1 ^ 00 plane), so that the N-type semiconductor layer 11 20 formed on the sapphire substrate 10 does not generate a crystal defect. The depth and size of each recess 14 are 1 μm and 10 μm, respectively, and a pitch of 10 μm is defined by a center of each recess 14. Here, a plurality of convex portions 102 are formed on the sapphire substrate 10, which illustrates that the N-type semiconductor layer 11 grows from the epitaxial evolution of the sapphire substrate 10 over a 1236773 process. Referring to FIG. 2, the sapphire substrate 10 has a base surface 101 and a plurality of convex portions 102 protruding from the base surface 101 (only one convex portion 102 is shown in FIG. 2). When the N-type semiconductor layer η is grown on the sapphire substrate 10, the NH-type semiconductor layer 11 is grown from the base surface 101 and the top surface of the convex portion 102, and is located on the convex portion 102. The growth rate at the periphery is relatively slow. Referring to FIG. 3, when the N-type semiconductor layer 11 growing from the base surface 101 and the top surface of the convex portion 102 intersects, the growth speed of the N-type semiconductor layer at the intersection is accelerated. Finally, the N-type semiconductor layer 11 having excellent crystalliriity and no voids is formed flat. Referring to FIG. 1 'the design of the plurality of recesses 14 provided on the sapphire substrate has the following effects on the semiconductor light emitting element: First, the recesses 14 cause scattering or diffraction of the light source' And reduce the loss and absorption caused by lateral propagation and increase the external quantum efficiency of the semiconductor light emitting element. In addition, since no crystal defect is generated between the sapphire substrate 10 and the N-type semiconductor layer 11, internal quantum efficiency can be increased. In addition, since the N-type semiconductor layer 11 can completely bury the recesses 14 to avoid unnecessary closed holes from causing obstruction when the light source is scattered or diffracted. However, those who are familiar with the field of crystallography of materials all know that at the interface of different lattice constants, lattice mismatch will occur. In addition, as the contact area of two materials with different lattice constants increases and the thickness of the accumulated atomic layer increases, the density of differential rows (so-called line defects) accompanying the lattice mismatch phenomenon also follows. Becomes high. According to the concept of the above semiconductor light emitting element, the N-type half 1236773 conductor layer 11 can completely bury the recesses 14, which means that the contact area of both the sapphire substrate 10 and the N-type semiconductor layer u is large. Therefore, from the theory of crystallography, it can be known that the internal quantum efficiency of the semiconductor light emitting element will be greatly reduced due to a large amount of differential density and affect the external quantum efficiency of the semiconductor light emitting element. Therefore, how to achieve the high internal quantum efficiency of the light-emitting diodes while also taking into account the excellent external quantum efficiency is a major problem to be overcome by those involved in the research and development of light-emitting diodes. [Summary of the Invention] 10 Summary of the Invention The inventor is based on the principle of crystallography and uses the viewpoint of reducing the density of the differential row to improve the internal quantum efficiency of a semiconductor light emitting element. As shown in FIG. 4, a predetermined pattern having a plurality of grooves 901 is formed on a sapphire substrate 90 (but only one groove 901 is illustrated in FIG. 4), and the 15 steps of these grooves 901 are (SteP; also called the depth of the groove 901) is controlled to be less than 5 μm, and the size and pitch of the grooves 901 are respectively controlled to be less than 7 μm. In addition, the lateral epitaxial growth technology is used to control the epitaxial velocity in the transverse direction to be greater than the epitaxial velocity in the longitudinal direction, so that the semiconductor epitaxial crystal 902 (epitaxial 20 ( ^% 41) One of the growth stable planes is the crystal plane of the 彳 1120 face group (in FIG. 4, 疋 is represented by the 彳 1122 face group). Therefore, during the growth process, the semiconductor epitaxial crystal 902 is borrowed by A plurality of closed holes (903) can be defined together with the grooves 901 by the growth-stable surface (the crystal plane of the sacral plane group). The grooves 901 and 901 of the sapphire substrate 90 described above can be defined together with the grooves 901, respectively. It can be known that the closed holes 903 defined between the growth stable surface of the semiconductor epitaxial crystal 902, the inventor reduced the differential density by reducing the contact area between the sapphire substrate 90 and the semiconductor epitaxial crystal 902. And increase the internal quantum effect of the light source generated by the semiconductor epitaxial crystal 902 and increase the external quantum effect at the same time. In addition, the grooves 901 can form the diffraction and scattering of the light source, and reduce the loss caused by the lateral propagation. In addition, since the size of the closed holes 903 is less than 1 μη, the closed holes 9⑽ do not pose a problem of poor heat dissipation. DETAILED DESCRIPTION OF THE INVENTION Therefore, the object of the present invention is to provide a high-efficiency light-emitting element. The high-efficiency light-emitting element of the present invention includes a substrate and a stupid crystal formed on the substrate. The substrate has a base surface and a plurality of recesses recessed from the base surface of the substrate at intervals. The epitaxial crystal has A base surface and a plurality of convex pillars protruding from the base surface of the epitaxial crystal. The convex pillars of the epitaxial crystal are respectively arranged in the grooves of the substrate. Each groove of the substrate and each of the epitaxial crystals A convex pillar cooperates to define a plurality of closed holes. It is worth mentioning that although the high-efficiency light-emitting element of the present invention cooperates with the grooves on the substrate and the convex pillars on the epitaxial crystal to define the closed holes Holes to reduce the contact area between the substrate and the epitaxial crystal and reduce the difference in row density to achieve high internal quantum efficiency. In contrast, the closed holes of the high-efficiency light-emitting element of the present invention can also be It is to form a plurality of mutually spaced convex pillars on the 1237873 substrate, so that the stupid crystal epitaxially formed on the substrate has grooves recessed from the lower surface of one of the epitaxial crystals at intervals and is formed on the substrate. The convex pillars and the grooves on the epitaxial crystal cooperate to define the closed holes, so as to reduce the area of contact between the substrate and the epitaxial crystal5 and reduce the differential density, so as to achieve the characteristics of high internal quantum efficiency. The substrate of the invention is selected from the group consisting of: sapphire, silicon carbide (SiC), and silicon (Si). Preferably, the substrate is sapphire. In a specific example, the The base surface of the substrate is a C-plane of the sapphire, and the C-plane is a (0001) plane. 10 Preferably, the epitaxial crystal has a first-type semiconductor layer, a light-emitting layer partially covering the first-type semiconductor layer, and a second-type semiconductor covering the light-emitting layer in order from the substrate in a direction away from the substrate. Layer, the bumps of the epitaxial crystal are formed on the first type semiconductor layer. Preferably, the epitaxial crystal is made of a semiconducting compound containing a Dy group and a V group element. It is worth mentioning that, in the semiconductor compound containing El and V elements, which causes the epitaxial crystal of the high-efficiency light-emitting element of the present invention to generate a light source with a frequency between 700 nm and 550 nm, the melon group element is selected from In the group consisting of: aluminum (A1), gallium (Ga), indium (and one of these combinations; the group V element is selected from the group consisting of: 20 phosphorus (P) And arsenic (As). In addition, in a semiconductor compound containing Group II and Group V elements that causes a stupid crystal of the high-efficiency light-emitting element of the present invention to generate a light source having a frequency of 550 nm to 370 nm, the Group VIII element Selected from the group consisting of: aluminum (A1), gallium (Ga), indium (In), and one of these combinations; the group V element is nitrogen (N). In a specific example, the melon group Element 10 1236773 and the group v element are gallium (Ga) and nitrogen hafnium, respectively, that is, the semiconductor compound containing melons and group v elements is a semiconductor compound containing gallium nitride (referred to as rhenium). Type semiconductor layer is an n-type semiconductor layer 'The second type semiconductor layer is an M (p_type) half Conductor layer. Preferably, the high-efficiency light-emitting element of the present invention further includes a first contact electrode (eQntaet) formed on the first-type semiconductor layer, and a second contact formed on the second-type semiconductor layer. Electrode ... Preferably, the worm's sun is a hexagQnal crystal, and the basal plane of the worm_crystal is parallel to the basal plane of the substrate. Preferably, a growth stable surface of the epitaxial crystal is The 彳 112Z Bu face group is selected from the group consisting of: (ll2z), (l2lz), (2llz), (ll2z), (piz), and (2Hz). In a specific example, z is equal to Q. Therefore, in a specific example, the 彳 ll ^ z 丨 face group is a 彳 112 ° face group. The face group is selected from the group consisting of: (11 彡 〇), (1 土 1〇) , (2110), (Π20), (00), and (2 ^ 0). _ Preferably, the grooves on the substrate are arranged in an array s (array) _.-Preferably, the substrate Each groove has a predetermined depth between 0.5 μm and 5 μ [η. Preferably, each groove of the substrate has a pre-distance between 2 111 111 and 7 μιη. Fixed size. A predetermined distance between 2 μm and 7 μm is defined by a center of each groove of the substrate. It is worth mentioning that the grooves on the substrate are set by a 1236773 The substrate has a mask with a predetermined pattern, which is formed by photolithography. Preferably, the predetermined pattern is selected from the group consisting of an array of circles Shapes, arrays of equilateral quadrilaterals, arrays of equilateral hexagons, and arrays of equilateral triangles. In a specific example, the predetermined pattern is a circle arranged in an array. The effect of the present invention is that the area of contact between the substrate and the epitaxial crystal is reduced by the closed holes to reduce the differential density, and the light emitting device of the present invention achieves high internal quantum efficiency. [Embodiment] Regarding the present invention, other technical contents, features, and effects will be clearly understood in the following detailed description with reference to one specific example of the accompanying drawings. <Specific Example> Referring to FIG. 5, a specific example of the high-efficiency light-emitting element of the present invention includes:-a sapphire substrate 2,-an epitaxial crystal 3 formed on the sapphire substrate 2, and a Ti / Al / Ti / Au contact The electrode 41 and a Ni / Au contact electrode 42. The sapphire substrate 2 has a base surface 21 having a (00 01) plane, and a plurality of grooves 22 recessed from the base surface 21 of the substrate 2 at intervals. Each groove 22 has a depth of 1.5 μm and a size of 3 μm. A center of each groove 22 defines a distance of 3 μm. Wherein, a mask (not shown) having a circular pattern arranged in an array is formed on the sapphire substrate 2 and the grooves 22 are formed on the sapphire substrate 2 by a dry etching method. In order to make 12 1236773, the sapphire substrate 2 with the grooves 22 is shown (as shown in FIG. 6). The GaN stupid crystal 3 has a base surface 31 having a (0001) plane and a plurality of convex pillars 32 protruding from the base surface 31 of the GaN epitaxial crystal 3. The convex pillars 32 of the GaN cat crystal 3 are respectively disposed in the grooves 5 22 of the sapphire substrate 2. Each groove 22 of the sapphire substrate 2 cooperates with each protrusion 32 of the GaN stupid crystal 3 to define a plurality of closed holes 5. The GaN epitaxial crystal 3 recedes from the GaN substrate 3 to the square φ of the GaN substrate 3, and sequentially has an η-GaN semiconductor layer 33, a light-emitting layer 34 partially covering the n-GaN semiconductor layer 33, and a cover layer The p-GaN semiconductor layer 35 of the light emitting layer 34. Among them, the bulge 32 of the GaN worm crystal 3 is formed on the η-GaN semiconductor layer 33. Here, the η-GaN semiconductor layer 33 formed on the sapphire substrate 2 is used to control the epitaxial speed of the η-GaN semiconductor layer 33 in the lateral direction to be greater than that in the longitudinal direction, so that it is located on the sapphire. One of the η-GaN semiconductor layers 33 at the difference step of the groove 22 of the substrate 15 and the plate 2 is a 彳 ii2 (U face group group. By using the 彳 π20〇 face group group, the epitaxial layer in the n_GaN semiconductor layer 33 is formed. In the process, the recesses # 22 are covered in a triangular shape along the periphery of the recesses 22 (this phenomenon can be seen in FIG. 7). From the foregoing and referring to FIG. 5, each recess 22 and The n-GaN semiconductor layer 33 formed on the sapphire substrate 2 can form three closed holes 5 (this phenomenon can be seen in FIG. 8). However, since FIG. 8 is the sapphire substrate 2 of this specific example 1 and A scanning electron microscope (scanmng eiectron micr_pe; referred to as a cross-section topography) between the n-GaN semiconductor layer 33 shows only two closed holes 5 of the three closed holes 5 described above, because 13 1236773 Therefore, the third closed hole 5 may be hidden behind the n-GaN semiconductor layer 33 located in the groove 22. Or the front side. The light emitting layer 34 has an n-AlGaN film 341 connected to the n-GaN semiconductor layer 33, a p-AlGaN 5 film 343 connected to the p-GaN semiconductor layer 35, and a sandwiched between the A multi-quantum quantum well (MQW) 342 between the n-AlGaN film 341 and the p-AlGaN film 343. The structure of the multi-layer quantum well 342 is (InGaN / GaN) n. The Ti / Al / Ti The / Au contact electrode 41 and the Ni / Au contact electrode 42 are formed on the η-GaN semiconductor layer 33 and the p-GaN semiconductor layer _ 1034, respectively. Referring to FIG. 9, they are formed on the η-GaN semiconductor layer. The relationship between the difference in row density and groove depth on layer 33. From Figure 9, it can be obtained that when the horizontal coordinate (groove depth) is larger, the relative vertical coordinate (differential row density) is smaller. See FIG. 10, which is formed in A differential force 15 atomic force microscope (AFM) —a morphology of the n-GaN semiconductor layer 33. FIG. 10 shows that the difference row formed on the n-GaN semiconductor layer 33 is six. The threading repair dislocation of the polygon has a scanning area of 5 μm χ 5 and the density of the difference row is less than 3 X 108cnT2. 20 See also Figure H is a comparison diagram of the current-to-voltage relationship between the light-emitting element and a conventional light-emitting element (meaning a traditional light-emitting diode) of this specific example. As can be obtained from Figure 11, the reverse direction of this specific example when the voltage is -5V The leakage current (Ir) is much smaller than the reverse leakage current value of the traditional light-emitting diode, which is only 0.24 nA. The result indicates that the leakage current value of this specific example is 14 1236773. Referring to FIG. 12, a comparison diagram of the relationship between the output power and the current of the light source of the specific example and the light source of the conventional light emitting diode is shown. The results show that, under the same output current value, the light-emitting element of the specific example has a higher output power of the light source 5. The reason is that the differential density of the light-emitting element of the specific example is low, so the light-emitting element The internal quantum efficiency of the light source generated by the layer 33 is higher. From the foregoing, the high-efficiency light-emitting element of this specific example has a higher internal quantum efficiency, and therefore also increases the external quantum efficiency and has a higher light source output power value. 10 Refer to Figure 丨 3 for a comparative analysis of the electroluminescence spectrum (EL · spectrum) for different current injection values. Because, one of the main causes of the wavelength shift of a light emitting diode is the poor heat dissipation. However, an excessively large closed hole space between the sapphire substrate and the n_GaN semiconductor layer is one of the causes of poor heat dissipation. As shown in Figure 15 and Figure 13, when comparing a conventional light-emitting diode with a sapphire substrate with a 1.5 μm groove depth pattern, the wavelength shift is almost the same. The closed hole in the light emitting element does not affect the heat dissipation of the element. To sum up, the high-efficiency light-emitting element of the present invention has the characteristics of 20 差 difference density, high internal efficiency, small leakage current, good heat dissipation, and high light source output power, and indeed achieves the purpose of the present invention. However, the above are only the preferred embodiments of the present invention. When the scope of implementation of the present invention cannot be limited by this, that is, the simple equivalent changes and modifications made according to the scope of the patent application and the content of the invention specification, Both 15 1236773 should still fall within the scope of the invention patent. [Brief description of the figure] A schematic diagram of a front view of JL 疋, illustrating the luminescence of a bull conductor. Figure 2 is a schematic and cross-sectional view of a front view, illustrating one of the conventional n-type semiconductor layers growing on the epitaxial evolution of a sapphire substrate. Figure 3 is a schematic cross-sectional front view illustrating the conventional n-type semiconductor layer growing after the epitaxial evolution process of the sapphire substrate; 15 20 Figure 4 is a schematic diagram of a bug crystal evolution, illustrating the inventive concept of the present invention; FIG. 5 is a schematic front view illustrating a specific example of the high-efficiency light-emitting element of the present invention; FIG. 6 is a top-view SEM view illustrating a groove on a sapphire substrate of the specific example; FIG. 7 is a SEM shape A diagram showing the relationship between an n-semiconductor layer and the grooves of the sapphire substrate during an epitaxial process; FIG. 8 is a SEM cross-sectional morphology diagram; FIG. 9 is a diagram of a difference in row density versus groove depth; 10 is an AFM morphology diagram; FIG. 11 is a current-to-voltage relationship comparison diagram; FIG. 12 is a light-source output power-to-current relationship diagram; and FIG. 13 is a comparison of the peak-wavelength relationship of different current injections Illustration. 16 1236773 [Simplified explanation of the main symbols of the drawings] 2 ........., ... Sapphire substrate 343… ·,… · ρ-AlGaN film 21 …….… Base surface 35 ……. …… p-GaN semiconductor layer 22 ………… grooves 41 ………… Ti / Al / Ti / Au contact electrode 3 ………… * GaN sun body 42 …… 《…… Ni / Au contact electrode 3… ...... basal surface 5 ...... ...... closed hole 32 ……… bulge 90 …… sapphire Substrate 33 ... ···· n GaN semiconductor layer 901 ...... ···· groove 34 …… ........ light emitting layer 902…… .. “Η-AlGaN film 903…… closed hole 342… .. • multilayer quantum well 17