1249256 九、發明說明： 【發明所屬之技術領域】 本發明係有關於一種具有多重發光層之發光二極體結構，更特別地 是一種形成具有多重發光層之發光二極體結構的方法。 【先前技術】 發光二極體之應用頗為廣泛，例如，可應用於光學顯示裝置、交通 號誌、資料儲存裝置、通訊裝置、照明裝置、以及醫療裝置。發光二極體 中潛在需求量最大、且最重要者，為白色光發光二極體，若是能夠降低白 色光發光一極體的生產成本，並且增成其使用壽命，則有可能取代目前大 量使用之白色螢光燈管或是燈泡。 目前市面上最常見的白色光發光二極體是由藍色光發光二極體與螢 光材料組合而成，其原理係利用藍色光發光二極體晶粒所發射之藍色光激 發螢光材料，使知後者產生黃光，而黃色光與原來的藍色光混合，而成為 白色光。在習知技術中，白色光發光二極體的主要缺點在於:藍色光發光二 極體晶粒雖然有約十萬小時的壽命，但是會由於採用螢光材料，而造成此 種白色光發光二極體的整體壽命大為縮短。 此外，在此習知技術中，白色光發光二極體的另一個缺點乃是在於， 必須由藍色光發光二極體與螢光材料組合，因而造成複雜的製造程序，進 而導致南昂的生產成本。 另外，在習知技術中形成白色光光源的方法包含以下幾種，一種是由 曰本曰亞化學公司(Nichia Chemical)發展出以氮化銦鎵藍色光發光二極 體，配合發射黃色光之釔鋁石榴石型螢光粉aluminum 1249256 garnet，YAG)，亦可以成為一白色光光源。此種方法的發光效率可以達到 20 lm/W，因為只須要一組發光二極體晶片即可，所以大幅度地降低製造 成本，再加上所搭配的螢光粉調製技術已漸成熟，故在市面上已有商品呈 現。 此種產生白色光的方法，是利用互補色的原理來產生白色光，其光譜 波長分佈的連續性不如真實的太陽光，使得藍色光與黃色光混合後會在可 見光光譜範圍(大約400nm〜700nm)出現色彩的不均勻，導致色彩飽和度 較低；雖然人類的眼睛可以忽略這些現象，只會看見白色光，但在一些精 密度較高的光學偵檢器的感測下，例如，攝影機或是相機等等，其演色性 在實質上仍偏低，亦即物體色彩在還原時會產生誤差，所以這種方式產生 的白色光光源只適合作為簡單的照明用途〇 另一種形成白色光發光二極體的方法，是由習知的三波長型白色光光 源’在製作時為了提咼其演色性，一般是使用三種或是三種以上的螢光粉。 而欲同時利用多種螢光粉體使其發出螢光，先決條件之一乃是所選用之激 發光(一紫外光源），恰可以被這些螢光粉體所吸收，且各種螢光粉體對此波 長的光的吸收係數不能相差太多，連同光能轉換的量子效率也盡可能接近 為佳。因此，限制了可以適用的螢光材料種類，造成選用螢光材料的困難。 且根據混色原理，使用三種或以上的螢光粉，其混色方程式為二次以上方 程式，此為非線性方程式，因此其顏色的變化率為二維以上。所以在調配 三原色螢光粉的比例以得到白色光的技術上相當的困難。 【發明内容】 為了改善習知技術中產生白色光發光二極體之各種缺點，於此提供一 種具有多重發光層之單石型(m〇ln〇lithic)發光二極體結構，在不須搭配螢 光粉體，即可達到產生白色光之功效。 1249256 本發明的目的在於提供-鮮重發錢之發光二鋪結構， 配螢光粉體的條件下，產生白色光。 册 本發明的目的’係姻高温及低溫兩織程形成至少具有_不同發 光顏色的多光發光層，根據顏色混成的輕，使得兩種不同發光顏色 光層所產生的色光混合，以產生白色光。 根據以上所述之目的，本發明提供了一種多重發光層之發光二極體結 構’其中包含具有-平滑表面之基板…第―摻雜型氮化鎵層位於基板的 平滑表面上方、以氮化銦鎵為主的第一發光層位於第一摻雜型氮化鎵層上 方-以氮化銦鍊為主的第一發光層位於第一發光層上方，以及一第二摻雜 型氮化鎵位於第二型發光層的上方。其中，以氮化銦鎵為主的第一發光層 為藍色光發光層，而以氮化銦鎵為主的第二發光層為黃色光發光層。當第 一發光層被注入電荷載子時，會產生藍色光，且此藍色光會穿透至第二發 光層時’使得藍色光和第二發光層產生之黃色光可以混合，而產生白色光。 另外，根據以上之結構，本發明提出形成具有多重發光層之發光二極 體結構之方法，包含提供具有一平滑表面之基板，在高溫製程條件下，在 基板的平滑表面上方形成以氮化鎵成份為主的第一摻雜型氮化鎵層，其形 成的方法例如’有機金屬氣相沉積法(Metal Organic Chemical Vapor Deposition，MOCVD)。接著，在第一摻雜型氮化鎵層上形成發藍色光、 且以氮化銦鎵成份為主的第一發光層，其形成的方法例如，有機金屬氣相 沉積法。相對於第一摻雜型氮化鎵層以及第一發光層的形成方法，在第一 發光層上方以低溫製程，形成具有銦含量較多的第二發光層，其形成的方 法例如·電漿輔助式分子束蠢晶法(Plasma-Assisted Molecular Beam Epitaxy ’ PAMBE)或電毁加強式化學氣相沈積法(Plasma-Enhanced Chemical Vapor Deposition，PECVD)。 然後’在第二發光層上方形成第二摻雜型氮化鎵層，其形成的方法例 1249256 如，電漿輔助式分子束磊晶法或電漿加強式化學氣相沈積法。其中，第一 發光層為藍色光發光層，藉由注入電荷載子而產生藍色光，而藍色光穿透 過第二型發光層，可與第二發光層產生之黃岜光混合而產生白色光。 本發明知:供另一種具有多重發光層之單S(m〇n〇l奸hic)發光二極體結 構，包含具有上、下表面均為平滑表面之基板，於透明基板的下表面具有 第一發光層之發光二極體晶粒之結構；以及位於透明基板的上表面，具有 高銦成份(high-In-content)的第二發光層。當位於透明基板下表面的發光 二極體加上順向電壓時，會發射出色光，例如藍色光，此色光會透過透明 基板，到達第二發光層，並且激發高銦成份的第二發光層，由於高銦成份 的第二發光層受到短波長色光的激發，會產生另一具有較長波長之色光， 例如黃色光。因此，藍色光與黃色弋會產生混合，而產生白色光。 又根據以上多重發光層之發光二極體結構，其形成的方法包含，提供 具有上、下表面均為平滑表面之透明基板，於透明基板之下表面，形成具 有第一型發光層之發光二極體晶粒。接著，於透明基板之上表面，以低溫 製程條件’形成以面姻成份之氮化麵嫁第二發光層；之後，於該第二發光 層上方，形成一氮化鎵層。藉由發光二極體發射出較短波長之色光，此色 光穿透過基板至第二發光層，使得第二發光層被光激發產生較長波長之色 光，然後，由發光二極體所發射的較短波長之色光與此較長波長之色光混 合，而產生具有各種波長之不同顏色的色光。 【實施方式】 本發明的一些實施例會詳細描述如下。然而，除了詳細描述外，本發明還 可以廣泛地在其他的實施例施行，且本發明的範圍不受限定，其以 之後的專利範圍為準。 根據習知技術中，欲形成白色光發光二極體須藉由搭配螢光粉體才能 1249256 達到。但是由於調配螢光粉體的過程為相當繁雜之步驟，因此，本發明提 供一種不須使用螢光粉體，而可以產生白光光源之發光二極體。 首先要說明的是，第一 A圖至第一 B圖是用來表示，本發明所揭露 具有多發光層之發光二極體結構之一較佳實施例之步驟及結構側示圖。第 二A圖至第二C圖係用來表示，本發明所揭露具有多重發光層之發光二極 體結構之另一較佳實施例之步驟及結構側示圖。 請參閱第一 A圖及第一 B圖，根據本發明之較佳實施例，具有多重 發光層之發光二極體結構包含：具有一平滑表面12之基板1〇 ; 一第一摻 雜型氮化鎵層20，例如η型氮化鎵層，位於基板1〇的平滑表面12上方； 第一發光層22位於第一摻雜型氮化鎵層2〇的上方；第二發光層3〇位於 第一發光層22的上方；以及第二摻雜型氮化鎵層32，例如，ρ型氮化嫁 層，位於第二發光層30的上方。 根據以上之結構，第一發光層22，主要是以含有較少量的銦成份為 主的氮化銦鎵(InxGai-xN)，其中，銦成份的含量約為ΐ5~20%。其結構可 以是單層或是多層量子井(quantum weU)，又或者是雙異質(d〇uble heterostructure)。另外，第二發光層30，主要是含有較多量的銦成份為 主的敗化銦鎵(InxGai-xN)，其銦成份的含量大於30%。基板1〇通常是以 藍寶石(sapphire)，或者是以導電之石夕(Si)或碳化矽(sic)做為基板1〇的主 要材料。 根據以上之結構，本發明揭露一種形成具有多重發光層之發光二極體 的方法，首先提供具有一平滑表面12之一基板1〇。接著，在高溫製程中， 在基板10的平滑表面12上，形成具有摻雜石夕(d〇ped-Si)之第一摻雜型(η· 型)氮化鎵層20。其中，形成的方法例如，有機金屬氣相沉積(metal 〇rganic chemical vapor deposition，MOCVD)，其製程溫度約為 1000〜1100°c。之後，仍然在高溫製程，在第一摻雜型氮化鎵層2〇上方， 1249256 形成第一發光層22，其形成的方法例如，有機金屬氣相沉積法，其製程溫 度約為700〜800°C。 在本發明之較佳實施例中，第一發光層22中的成份為含有較少量銦 成份的氮化銦鎵，其結構可以是單層或是多層量子井層(multiple quantum wells)所構成之發光層，另外也可以是雙異質結構。因此，在第 一發光層22被電激發時，會產生藍色光，其藍色光的波長約為430奈米 (nm)至 470 奈米(nm)。 在此要說明的是，在習知的有機金屬氣相沉積技術中，由於採用氨 (ammonia，NH3)及三族(group III)有機金屬前驅物(precursors)以沉積三 族氮化物半導體，因此，沈積時之基板温度須夠高，以便裂解氨與三族有 機金屬前驅物，以長出氮化物磊晶膜。由於高銦成份(含量大於3〇〇/0)的氮 化銦鎵’在高温時不穩定，習知的有機金屬氣相沉積技術僅能被用來成長 低銦成份(15-20%)的氮化銦鎵。除此之外，經由有機金屬氣相沉積技術產 生之第二摻雜型(Ρ-型)氮化鎵層須活化鎂(Mg)摻雜物以產生ρ-型載子，而 此步驟通常採用一高温退火的除氫動作。但是有機金屬氣相沉積技術目前 具有已制式化、高成長速率及優良磊晶品質等優勢。相對而言，電漿輔助 式分子束磊晶法或電漿加強式化學氣相沈積法由於採用活性甚高之氮電漿 源(anitrogen Plasma)，可在低温條件(55〇〜65〇t：)成長高銦成份(含量大於 35%)的氮化銦鎵。電漿辅助#分子束蠢晶法更由於是在低氩環境下成長摻 鎮之第二摻雜型(p-型)氮化鎵層，以經過實驗證實，可不經高温退火的除氫 過程直接在650°C的低成長温度下，長出高型載子濃度之氮化鎵膜。 本發明所揭露之第二發光層3〇及第二摻雜型(p-型)氮化鎵層32，由 於^兩段式製齡财，係在低溫餘下，紐黄色光之齡銦鎵層及第 :糝雜型巾_型)氮化騎長在高溫製㈣狀健色光的氮化銦鎵層上 二〜得巧·色光之间銦成份(含量大於加。/…氮化銦嫁層的能隙批仏职切 會觉到高溫製程的影響，導致局部載子侷限能量位階之移動而造成混光 11 1249256 不均勻或錯誤之缺點。 因此，根據習知技術之缺點，本發明係先以高溫製程依序在基板10 上，形成第一摻雜型氮化鎵層20以及第一發光層22。因此，在後續步驟 中第一發光層22中的銦含量以及其發光能隙值，不會因為低溫製程步驟而 有所影響。 接著，在第一發光層22上方形成具有含有銦含量較多的第二發光層 3〇 ’其形成的方法例如，電漿輔助式分子束磊晶法(PAMBE)或電漿增強式 化學氣相沈積法(PECVD)，其製程溫度約為550~650°C，且該製程溫度與 形成第一發光層22相比較，為低溫製程。其中，第二發光層3〇可以是以 成份為高銦含量(high-In-content)之氮化銦鎵為主的單層、或者是多層量 子井層，亦或者是雙異質結構。第二發光層30與第一發光層22結構上之 差異乃是在於’第二發光層30的銦含量較多，使得第二發光層3〇被激發 時，可以發射出波長較長之黃色光，其波長約為550奈米至590奈米。接 著，在第二發光層30上方形成第二摻雜型氮化鎵層32，而形成第二掺雜 型氮化鎵層32的方法例如，低溫成長之電漿辅助式分子束磊晶法(pAMBE) 或電漿增強式化學氣相沈積法。 根據以上形成具有多重發光層之發光二極體結構，可以得知，藉由含 有少量銦成份之第一發光層以及銦含量較多之第二發光層結合，可使得藍 色光和黃色光兩個色光可以混和以產生白色光。此方法的優點在於，利用 銦含量的多寡會影響發光層的發光特性，使得具有不同銦含量的發光層會 產生不同的色光，藉由混合不同銦含量的發光層的色光，而得到使用者所 須要的色光。 另外，本實施例的優點是在於，在具有多重發光層之發光二極體的結 構内不須要搭配螢光粉體，或者是藉由螢光粉體的調配，即可達到混和色 光之目地。此外，藉由高溫製程，將較難以與基板有良好之晶袼匹配之第 12 1249256 摻雜型氮化鎵層’形成在基板上方，且以氮化銦鎵為主的第_發光層内 由銦含量不會因為後續之步驟，而產生能隙值變動的影響。因此，可以藉 具有多重發光層之發光二極體結構產生混和良好之混合色光之發光二極 體結構。 另外，在本發明揭露另一較佳實施例，其主要目地仍然是為了形成混 色良好之白色光之發光二極體。，具有多重發光層之發光二極體包含一透 明基板50，其透明基板50的上表面52以及下表面54均為平滑表面；具 有第一發光層之發光二極體結構6〇，位於透明基板5〇的下表面54 ; 一緩 衝層80位於基板50的上表面52 ; —第二發光層82位於緩衝層80的上 方；以及一氮化鎵層84位於第二發光層82上方。 明參閱第一 A圖’在透明基板50的下表面54具有一發光二極體結 構60。請參閱第二b圖，其發光二極體結構6〇,可以是一般發光二極體 晶粒’其發光顏色可以由藍色光到紫外光，係由緩衝層62、第一摻雜型氮 化鎵層64、第一發光層66、第二摻雜型氮化鎵層68、第二型電極70、 以及第一型電極72所構成。其中，第一發光層60所發射的色光可以是藍 色光到紫外光。在本實施例中，是以含較低銦成份之氮化銦鎵為主的藍色 光發光層，而其第一發光層的可以是單層或多層量子井，亦或是雙異質結 構0 在此要說明的是，為了便於說明，第二B圖係為發光二極體晶粒之正 視圖，但是在本實施例中，其結構則是倒視圖。此外，在本實施例中，僅 以藍色光發光二極體之結構來做說明，然而其發光二極體晶粒的種類並不 在此限制。 請參閱第二C圖，一氮化鎵緩衝層80位於透明基板50的上表面52; 一第二發光層82位於緩衝層80的上方，其主要成份是以含有較多銦成份 之氮化銦鎵為主，其結構可以是單層或是多層量子井，又或者是具有雙異 13 1249256 質結構。之後’一氮化鎵層84位於第二發光層82的上方 根據以上結構，本發_露_種形成具有多重發光層 構的方法，找提供具有上表面52以及下表面54均為平滑表面 板50。接著’以-般形成發光二極體結構之步驟，於透明基板5 二 面54先形成緩衝層62 ’然後在高溫步驟中於緩衝層62上方成長 雜型氮化鎵層64。接著’於第-摻雜魏化鎵層64上方形成^發 66 ’其形方法例如，有機金屬化學氣相沉積法，其 ^ ^ 700~800。(： 〇 馮 然後，在第-發光層66上方，形成一第二摻雜型氮化鎵層68。之後， 為了形成_麵，係以侧的对，依序移除部份的第二摻_型氮化 鎵層68、第二發光層66以及第-摻雜型氮化鎵層64，並曝露出部份的第 -摻雜型氮化鎵層64。接著，於曝露出的第二摻雜型氮化鎵層⑽的部份， 形成-第三型電極7G，於第-摻雜型氮化鎵層64上方形成—第_型電極 72，以完成具有歐姆接觸之藍色光發光二極體結構6〇。其中第一型電極 72可以是鈦/鋁(Ti/Al)或鈦/鋁/鎳/金(Ti/A1/Ni/Au)合金，而第二型電極 70可以是鎳/金(Ni/Au)合金。 接著，於透明基板50的上表面52形成一氮化鎵緩衝層8〇 ;之後， 於氮化鎵緩衝層80上方，形成含有較多銦成份之第二氮化銦鎵發光層 82，其形成的方法例如，電漿輔助式分子束磊晶法(pAMBE)或電漿增強式 化學氣相沈積法(PECVD)，其製程溫度約為55〇〜65(rc。然後，在第二發 光層82的上方形成一氮化鎵層84 ,其形成的方法例如，低溫成長之電漿 輔助式分子束蠢晶法或電紫增強式化學氣相沈積法。第二氮化銦嫁發光層 82之形成方法亦可藉由晶圓鍵合法(wafer bonding method)，將具有第 二發光層82之磊晶結構與具有第一發光層之發光二極體結構60鍵合。 藉由位於透明基板50下方的發光二極體6〇，經由施加電壓至第二型 1249256 電極70以及第一型電極72，使得位於發光二極體60内的第一發光層66 產生色光，例如藍色光’所產生的藍色光穿透過透明基板50，並且照射到 第二發光層82中，使得第二發光層82被激發，而產生色光，例如黃色光。 因此，所發射出的黃色光可以與藍色光結合，即可產生白色光。其優點在 於，直接利用發光層發光之原理，藉由短波長光之激發，使得不同銦含量 的發光層產生不同的發光顏色，使得兩種顏色色光產生混和，而得到所須 要的混合色光。 另外，在本實施中，不須要摻雜螢光粉體，或是調配螢光粉體即可以 達到混色色光的目的。因此，根據本實施例，在透明基板50的下表面54， 可以藉由形成具有不同發光顏色之發光二極體晶粒，且在導通一電麼而產 生發光顏色之後，穿透過透明基板50以及位於透明基板50上的第二發光 層82，以激發第二發光層82而發光，藉由第二發光層82中銦成份含量 的多养及第一發光層82之層厚，所產生的混光顏色也會隨著第二發光層 82之銦含篁及層厚的改變而作全色光域(fu]| c〇i〇r range)的改變。 以上所述僅為本發明之較佳實施例而已，並非用以限定本發明之申請 專利範圍，凡其它未脫離本發明所揭示之精神下所完成之等效改變或修 飾，均應包含在下述之申請專利範圍内。 【圖式簡單說明】 第一A圖至第一 B圖為根據本發明所揭露之技術，形成具有多色發光 層之發光二極體時，各步驟及結構側示圖； 第二A圖係根據本發明所揭露之技術，在透明基板之下表面形成藍色 光發光二極體時，各步驟及結構側示圖； 第一 B圖係根據本發明所揭露之技術，形成藍色光發光二極體之結構 15 1249256 正視圖；以及 第二c圖係根據本發明所揭露之技術，形成具有多色發光層之發光二 極體時，另一較佳實施例之各步驟之結構側示圖。 【主要元件符號說明】 10 基板 20 第一摻雜型(P型)氮化鎵層 30 第二發光層 50 透明基板 54 下表面 62 緩衝層 66 第一主動層 70 第二型電極 80 緩衝層 84 氮化鎵層 12上表面 22第一發光層 32第二摻雜型(η型)氮化鎵層 52上表面 60發光二極體晶粒 64第二摻雜型氮化鎵層 68第二摻雜型氮化鎵層 72第一型電極 82第二主動層BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light-emitting diode structure having multiple light-emitting layers, and more particularly to a method of forming a light-emitting diode structure having multiple light-emitting layers. [Prior Art] Luminous diodes are widely used, for example, in optical display devices, traffic signs, data storage devices, communication devices, lighting devices, and medical devices. The most potential and most important component of the light-emitting diode is a white light-emitting diode. If it can reduce the production cost of the white light-emitting body and increase its service life, it may replace the current large-scale use. White fluorescent tube or light bulb. At present, the most common white light-emitting diode on the market is a combination of a blue light-emitting diode and a fluorescent material. The principle is to use the blue light emitted by the blue light-emitting diode crystal to excite the fluorescent material. It is known that the latter produces yellow light, and the yellow light mixes with the original blue light to become white light. In the prior art, the main disadvantage of the white light emitting diode is that although the blue light emitting diode die has a life of about 100,000 hours, it will be caused by the use of a fluorescent material. The overall life of the polar body is greatly shortened. In addition, another disadvantage of the white light-emitting diode in this prior art is that it must be combined with a fluorescent material by a blue light-emitting diode, thereby causing a complicated manufacturing process, which in turn leads to the production of Nanang. cost. In addition, the method for forming a white light source in the prior art includes the following ones, one is developed by Nichia Chemical, an indium gallium nitride blue light emitting diode, which is combined with a yellow light emission. Yttrium aluminum garnet type fluorescent powder aluminum 1249256 garnet, YAG), can also be a white light source. The luminous efficiency of this method can reach 20 lm/W, because only one set of light-emitting diode chips is needed, so the manufacturing cost is greatly reduced, and the matching phosphor powder modulation technology is gradually matured. There are already products on the market. The method of generating white light is to use the principle of complementary color to generate white light, and the spectral wavelength distribution is not as continuous as real sunlight, so that the blue light and the yellow light are mixed in the visible light spectrum range (about 400 nm to 700 nm). ) uneven color, resulting in low color saturation; although human eyes can ignore these phenomena, only white light is seen, but under the sensing of some highly sophisticated optical detectors, for example, cameras or It is a camera, etc., its color rendering is still low in nature, that is, the color of the object will produce errors when it is restored, so the white light source produced by this method is only suitable for simple lighting purposes, and the other is to form white light. The polar body method is a three-wavelength white light source of the conventional one. In order to improve the color rendering property, three or more kinds of phosphor powders are generally used. One of the prerequisites for using a plurality of phosphor powders to emit fluorescence at the same time is that the selected excitation light (an ultraviolet light source) can be absorbed by the phosphor powder, and various phosphor powder pairs are used. The absorption coefficients of light at this wavelength cannot differ too much, and the quantum efficiency of the conversion of light energy is also as close as possible. Therefore, the types of fluorescent materials that can be applied are limited, which makes it difficult to select fluorescent materials. According to the color mixing principle, three or more kinds of phosphor powders are used, and the color mixing equation is a quadratic upper formula, which is a nonlinear equation, so the color change rate is two or more. Therefore, it is technically quite difficult to mix the ratio of the three primary color phosphors to obtain white light. SUMMARY OF THE INVENTION In order to improve various disadvantages of generating a white light emitting diode in the prior art, a monolithic (m〇ln〇lithic) light emitting diode structure having multiple light emitting layers is provided, which does not need to be matched. Fluorescent powder can achieve the effect of producing white light. 1249256 The object of the present invention is to provide a light-emitting two-story structure with fresh light and money, which produces white light under the condition of a fluorescent powder. The object of the present invention is to form a multi-photoluminescence layer having at least _ different illuminating colors according to the light mixing of the colors, so that the color lights generated by the two different illuminating color layers are mixed to generate white. Light. According to the above object, the present invention provides a light-emitting diode structure of a multiple light-emitting layer, which comprises a substrate having a smooth surface. The first doped gallium nitride layer is located above the smooth surface of the substrate to be nitrided. a first luminescent layer mainly composed of indium gallium is disposed above the first doped GaN layer - a first luminescent layer mainly composed of an indium nitride chain is located above the first luminescent layer, and a second doped GaN Located above the second type of luminescent layer. The first light-emitting layer mainly composed of indium gallium nitride is a blue light-emitting layer, and the second light-emitting layer mainly composed of indium gallium nitride is a yellow light-emitting layer. When the first luminescent layer is injected into the charge carrier, blue light is generated, and when the blue light penetrates into the second luminescent layer, 'the blue light and the yellow light generated by the second luminescent layer can be mixed to generate white light. . In addition, according to the above structure, the present invention proposes a method of forming a light emitting diode structure having multiple light emitting layers, comprising providing a substrate having a smooth surface, and forming gallium nitride over the smooth surface of the substrate under high temperature process conditions. A first doped gallium nitride layer mainly composed of a composition is formed by a method such as 'Metal Organic Chemical Vapor Deposition (MOCVD). Next, a first light-emitting layer which emits blue light and is mainly composed of an indium gallium nitride composition is formed on the first doped gallium nitride layer, and a method of forming the same is, for example, an organometallic vapor deposition method. With respect to the first doped gallium nitride layer and the first light emitting layer forming method, a second light emitting layer having a large indium content is formed on the first light emitting layer by a low temperature process, and a method of forming the film, for example, a plasma Plasma-Assisted Molecular Beam Epitaxy 'PAMBE or Plasma-Enhanced Chemical Vapor Deposition (PECVD). Then, a second doped gallium nitride layer is formed over the second light-emitting layer, and the method of forming it is, for example, a plasma-assisted molecular beam epitaxy or a plasma-enhanced chemical vapor deposition method. The first light-emitting layer is a blue light-emitting layer, and blue light is generated by injecting charge carriers, and the blue light passes through the second-type light-emitting layer, and can be mixed with the yellow light generated by the second light-emitting layer to generate white light. The present invention is directed to another single S (light-emitting layer) light-emitting diode structure having multiple light-emitting layers, comprising a substrate having smooth surfaces on both upper and lower surfaces, and having a surface on the lower surface of the transparent substrate. a structure of a light-emitting diode die of a light-emitting layer; and a second light-emitting layer having a high-in-content on an upper surface of the transparent substrate. When the light-emitting diode on the lower surface of the transparent substrate is applied with a forward voltage, excellent light, such as blue light, is transmitted, which passes through the transparent substrate, reaches the second light-emitting layer, and excites the second light-emitting layer having a high indium composition. Since the second luminescent layer of the high indium composition is excited by the short-wavelength color light, another color light having a longer wavelength, such as yellow light, is generated. Therefore, blue light and yellow enamel will mix and produce white light. According to the above light-emitting diode structure of the multiple light-emitting layer, the method for forming comprises: providing a transparent substrate having smooth surfaces on both upper and lower surfaces, and forming a light-emitting layer having a first-type light-emitting layer on a lower surface of the transparent substrate Polar body grain. Next, a second luminescent layer is formed on the upper surface of the transparent substrate by a low-temperature process condition to form a nitriding surface with a surface component; and then a gallium nitride layer is formed over the second luminescent layer. Light-emitting light of a shorter wavelength is emitted by the light-emitting diode, and the color light penetrates through the substrate to the second light-emitting layer, so that the second light-emitting layer is excited by light to generate color light of a longer wavelength, and then emitted by the light-emitting diode The shorter wavelength color light is mixed with the longer wavelength color light to produce colored light of different colors having various wavelengths. [Embodiment] Some embodiments of the present invention will be described in detail below. However, the present invention may be widely practiced in other embodiments, and the scope of the present invention is not limited by the scope of the following patents. According to the prior art, the white light emitting diode to be formed must be matched with the phosphor powder to reach 1249256. However, since the process of blending the phosphor powder is a rather complicated step, the present invention provides a light-emitting diode which can generate a white light source without using a phosphor powder. First of all, the first to the first B are used to show the steps and structural side views of a preferred embodiment of the light emitting diode structure having the multi-emissive layer disclosed in the present invention. 2A through 2C are diagrams showing the steps and structural side views of another preferred embodiment of the light emitting diode structure having multiple light emitting layers. Referring to FIG. 1A and FIG. 2B, in accordance with a preferred embodiment of the present invention, a light emitting diode structure having multiple light emitting layers includes: a substrate 1 having a smooth surface 12; a first doped nitrogen The gallium layer 20, for example, an n-type gallium nitride layer, is located above the smooth surface 12 of the substrate 1〇; the first light-emitting layer 22 is located above the first doped gallium nitride layer 2〇; the second light-emitting layer 3 is located Above the first luminescent layer 22; and a second doped gallium nitride layer 32, for example, a p-type nitriding layer, is located above the second luminescent layer 30. According to the above configuration, the first light-emitting layer 22 is mainly indium gallium nitride (InxGai-xN) mainly composed of a small amount of indium, wherein the content of the indium component is about ~5 to 20%. The structure may be a single layer or a multi-layer quantum well or a double heterostructure. Further, the second light-emitting layer 30 mainly contains a large amount of indium-doped indium gallium (InxGai-xN) having a content of indium of more than 30%. The substrate 1 is usually made of sapphire or is made of conductive Si (Si) or sic (sic) as the main material of the substrate. According to the above structure, the present invention discloses a method of forming a light-emitting diode having multiple light-emitting layers, first providing a substrate 1 having a smooth surface 12. Next, in the high temperature process, on the smooth surface 12 of the substrate 10, a first doped (n-type) gallium nitride layer 20 having a doped ped-Si is formed. Among them, the formation method is, for example, metal 〇rganic chemical vapor deposition (MOCVD), and the process temperature thereof is about 1000 to 1100 ° C. Thereafter, at a high temperature process, a first light-emitting layer 22 is formed over the first doped gallium nitride layer 2, 1249256, for example, an organometallic vapor deposition method having a process temperature of about 700 to 800 °C. In a preferred embodiment of the present invention, the composition of the first luminescent layer 22 is indium gallium nitride containing a relatively small amount of indium, and the structure may be a single layer or a plurality of quantum wells. The luminescent layer may also be a double heterostructure. Therefore, when the first luminescent layer 22 is electrically excited, blue light is generated, and the wavelength of the blue light is about 430 nm (nm) to 470 nm (nm). It is to be noted that in the conventional organometallic vapor deposition technique, since ammonia (NH3) and group III organometallic precursors are used to deposit a group III nitride semiconductor, The temperature of the substrate during deposition must be high enough to crack the ammonia and the tri-organic metal precursor to grow the nitride epitaxial film. Since indium gallium nitride with high indium content (content greater than 3 〇〇/0) is unstable at high temperatures, conventional organometallic vapor deposition techniques can only be used to grow low indium components (15-20%). Indium gallium nitride. In addition, the second doped (Ρ-type) gallium nitride layer produced by the organometallic vapor deposition technique must activate the magnesium (Mg) dopant to generate the p-type carrier, and this step is usually employed. A high temperature annealing dehydrogenation action. However, organometallic vapor deposition technology currently has advantages such as standardization, high growth rate and excellent epitaxial quality. In contrast, plasma-assisted molecular beam epitaxy or plasma-enhanced chemical vapor deposition can be used in low temperature conditions (55〇~65〇t due to the use of highly active atomic plasma). ) Indium gallium nitride with high indium content (content greater than 35%). The plasma-assisted #molecular beam stray method is more because it is a second doped (p-type) gallium nitride layer grown in a low argon atmosphere. It has been experimentally confirmed that the hydrogen removal process can be directly performed without high temperature annealing. At a low growth temperature of 650 ° C, a gallium nitride film having a high carrier concentration is grown. The second light-emitting layer 3〇 and the second doped type (p-type) gallium nitride layer 32 disclosed by the present invention are in the form of a two-stage type of age, and are in the low temperature remaining, and the yellow-light-aged indium gallium layer And the first: noisy towel _ type) nitriding ride on the high-temperature (four) shape of the light-colored indium gallium nitride layer two ~ decentive color between the indium components (content is greater than plus. /... indium nitride graft layer The gap of the energy gap will affect the influence of the high-temperature process, resulting in the localized carrier's limited energy level shifting, resulting in the unevenness or error of the mixed light 11 1249256. Therefore, according to the disadvantages of the prior art, the present invention is first Forming the first doped gallium nitride layer 20 and the first light emitting layer 22 on the substrate 10 in a high temperature process. Therefore, the indium content in the first light emitting layer 22 and the light emitting energy gap value thereof in the subsequent step, It is not affected by the low-temperature process step. Next, a method of forming a second light-emitting layer 3' having a large indium content is formed over the first light-emitting layer 22, for example, a plasma-assisted molecular beam epitaxy method. (PAMBE) or plasma enhanced chemical vapor deposition (PECVD) with a process temperature of approximately 550~650 ° C, and the process temperature is lower than that of forming the first light-emitting layer 22, wherein the second light-emitting layer 3 can be nitrided with high-in-content content. Indium gallium-based single layer, or multi-layer quantum well layer, or double heterostructure. The difference between the second luminescent layer 30 and the first luminescent layer 22 is that the indium content of the second luminescent layer 30 is lower. When the second luminescent layer 3 is excited, a longer wavelength of yellow light having a wavelength of about 550 nm to 590 nm can be emitted. Then, a second doping type is formed over the second luminescent layer 30. The gallium nitride layer 32 and the method of forming the second doped gallium nitride layer 32 are, for example, a plasma-assisted molecular beam epitaxy (pAMBE) or a plasma enhanced chemical vapor deposition method of low temperature growth. Forming a light-emitting diode structure having multiple light-emitting layers, it can be known that by combining a first light-emitting layer containing a small amount of indium component and a second light-emitting layer having a large indium content, two colors of blue light and yellow light can be made Blending to produce white light. The advantage of this method is that The amount of indium content affects the luminescent properties of the luminescent layer, so that luminescent layers having different indium contents produce different chromatic colors, and the color light of the luminescent layer of different indium contents is mixed to obtain the color light required by the user. The advantage of this embodiment is that the structure of the light-emitting diode having multiple light-emitting layers does not need to be matched with the phosphor powder, or the blending of the phosphor powder can achieve the purpose of mixing the color light. By the high temperature process, the 12 1249256 doped gallium nitride layer which is more difficult to match the substrate with a good crystal germanium is formed on the substrate, and the indium content of the first light emitting layer mainly composed of indium gallium nitride is formed. The influence of the variation of the energy gap value is not caused by the subsequent steps. Therefore, the light-emitting diode structure having the mixed light color with good multiple light-emitting layers can be used to produce a light-emitting diode structure with well-mixed mixed color light. Further, in the present invention, another preferred embodiment is disclosed, the main purpose of which is still to form a light-emitting diode of white light with good color mixing. The light emitting diode having multiple light emitting layers includes a transparent substrate 50, and the upper surface 52 and the lower surface 54 of the transparent substrate 50 are smooth surfaces; the light emitting diode structure having the first light emitting layer is disposed on the transparent substrate. A lower surface 54 of 5 turns; a buffer layer 80 is located on the upper surface 52 of the substrate 50; a second light-emitting layer 82 is located above the buffer layer 80; and a gallium nitride layer 84 is located above the second light-emitting layer 82. Referring to Fig. 1A', the lower surface 54 of the transparent substrate 50 has a light emitting diode structure 60. Please refer to the second b-picture, the LED structure 6〇, which can be a general light-emitting diode crystal ′, whose illuminating color can be from blue light to ultraviolet light, is buffer layer 62, and the first doped type is nitrided. The gallium layer 64, the first light-emitting layer 66, the second doped gallium nitride layer 68, the second-type electrode 70, and the first-type electrode 72 are formed. The color light emitted by the first luminescent layer 60 may be blue light to ultraviolet light. In this embodiment, a blue light emitting layer mainly composed of indium gallium nitride having a lower indium composition, and the first light emitting layer may be a single layer or a plurality of quantum wells, or a double heterostructure 0. It should be noted that, for convenience of explanation, the second B is a front view of the light emitting diode die, but in the embodiment, the structure is an inverted view. Further, in the present embodiment, only the structure of the blue light-emitting diode is explained, but the type of the light-emitting diode crystal grain is not limited thereto. Referring to FIG. 2C, a gallium nitride buffer layer 80 is located on the upper surface 52 of the transparent substrate 50. A second luminescent layer 82 is located above the buffer layer 80, and the main component thereof is an indium nitride containing a large amount of indium. Gallium is dominant, and its structure can be single-layer or multi-layer quantum wells, or it can have a double-different 13 1249256 structure. Then, the gallium nitride layer 84 is located above the second light-emitting layer 82. According to the above structure, the present invention forms a method having a multiple light-emitting layer structure, and provides a smooth surface plate having an upper surface 52 and a lower surface 54. 50. Next, the step of forming the light-emitting diode structure in a general manner is to form the buffer layer 62' on both sides 54 of the transparent substrate 5 and then grow the impurity-type gallium nitride layer 64 over the buffer layer 62 in the high temperature step. Next, a method of forming a pattern of a top surface of the first doped WeiGe layer 64 is performed, for example, an organometallic chemical vapor deposition method, which is ^ ^ 700 to 800. (: 〇 von then, above the first luminescent layer 66, a second doped GaN layer 68 is formed. Thereafter, in order to form the _ plane, the second pair is sequentially removed by the side pair a GaN-type gallium nitride layer 68, a second light-emitting layer 66, and a first-doped gallium nitride layer 64, and exposing a portion of the first-doped gallium nitride layer 64. Then, the exposed second A portion of the doped gallium nitride layer (10) forms a third-type electrode 7G, and a first-type electrode 72 is formed over the first-doped gallium nitride layer 64 to complete a blue light-emitting light having an ohmic contact. The polar body structure 6〇, wherein the first type electrode 72 may be titanium/aluminum (Ti/Al) or titanium/aluminum/nickel/gold (Ti/A1/Ni/Au) alloy, and the second type electrode 70 may be nickel. a gold (Ni/Au) alloy. Next, a gallium nitride buffer layer 8 is formed on the upper surface 52 of the transparent substrate 50. Thereafter, a second nitrogen containing a large amount of indium is formed over the gallium nitride buffer layer 80. The indium gallium luminescent layer 82 is formed by, for example, plasma assisted molecular beam epitaxy (pAMBE) or plasma enhanced chemical vapor deposition (PECVD), and has a process temperature of about 55 〇 to 65 (rc). .then A gallium nitride layer 84 is formed over the second light-emitting layer 82, and is formed by, for example, a plasma-assisted molecular beam stray crystal method or an electro-violet-enhanced chemical vapor deposition method of low temperature growth. The method of forming the graft light-emitting layer 82 may also bond the epitaxial structure having the second light-emitting layer 82 to the light-emitting diode structure 60 having the first light-emitting layer by a wafer bonding method. The light emitting diode 6A located under the transparent substrate 50 generates a color light, such as blue light, by applying a voltage to the second type 1249256 electrode 70 and the first type electrode 72, so that the first light emitting layer 66 located in the light emitting diode 60 generates color light. The generated blue light penetrates through the transparent substrate 50 and is irradiated into the second luminescent layer 82 such that the second luminescent layer 82 is excited to generate colored light, such as yellow light. Therefore, the emitted yellow light can be combined with blue The combination of color and light can produce white light. The advantage is that the light-emitting layer is directly illuminated by the excitation of short-wavelength light, so that the light-emitting layers with different indium contents produce different light-emitting colors, so that the two colors are The color light is mixed to obtain the desired mixed color light. In addition, in the present embodiment, the purpose of mixing the phosphor powder is not required, or the phosphor powder is blended to achieve the purpose of color mixing. Therefore, according to the embodiment, On the lower surface 54 of the transparent substrate 50, the transparent substrate 50 and the transparent substrate 50 can be penetrated by forming the light emitting diode crystal grains having different light emitting colors and generating the light emitting color after being turned on. The second light-emitting layer 82 emits light by exciting the second light-emitting layer 82. The multi-growth content of the indium component in the second light-emitting layer 82 and the layer thickness of the first light-emitting layer 82 also produce a mixed color. The indium of the second light-emitting layer 82 contains a change in the germanium and the layer thickness to cause a change in the full-color optical field (fu)|c〇i〇r range). The above are only the preferred embodiments of the present invention, and are not intended to limit the scope of the present invention. All other equivalent changes or modifications which are not departing from the spirit of the present invention should be included in the following. Within the scope of the patent application. BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1A to 1B are diagrams showing various steps and structures when forming a light-emitting diode having a multi-color light-emitting layer according to the technique disclosed in the present invention; According to the technology disclosed in the present invention, when a blue light emitting diode is formed on the lower surface of the transparent substrate, each step and structure side view; the first B picture is formed according to the technology disclosed in the present invention to form a blue light emitting diode The structure of the body 15 1249256 is a front view; and the second c is a structural side view of the steps of another preferred embodiment when forming a light-emitting diode having a multi-color light-emitting layer in accordance with the teachings of the present invention. [Main component symbol description] 10 substrate 20 First doped type (P type) gallium nitride layer 30 Second light emitting layer 50 Transparent substrate 54 Lower surface 62 Buffer layer 66 First active layer 70 Second type electrode 80 Buffer layer 84 Gallium nitride layer 12 upper surface 22 first light-emitting layer 32 second doped type (n-type) gallium nitride layer 52 upper surface 60 light-emitting diode die 64 second doped gallium nitride layer 68 second doped Miscellaneous gallium nitride layer 72 first type electrode 82 second active layer