本論文最主要藉由化學溶液濕蝕刻技術，製作具有倒金字塔側壁(inverted pyramid sidewall )的結構來減少光的全反射，並且增加光的散射以提高光取出效率，所以將此倒金字塔側壁結構應用於氮化鎵發光二極體之研究，並分析發光二極體的光電特性，希望可以有效提升發光元件之外部量子效率。 首先，必須於藍寶石基板成長高亮度的LED磊晶結構，再利用電漿輔助化學沉積系統(Plasma Enhance Chemical Vapor Deposition)在LED結構表面鍍上2μm厚度的二氧化矽膜作為混合酸蝕刻之遮罩後，使用黃光製程製作雷射切割道，需來利用雷射切割器(Laser Scribing)進行切割使氮化鎵與藍寶石基板中間的N面氮化鎵裸露出來，進而讓加熱的蝕刻液對裸露的N面氮化鎵進行蝕刻,最後會再LED側壁會形成倒金字塔側壁結構，則側壁被蝕刻的倒六角形金字塔角度會呈現58o。為了進一步確認蝕刻的機制，我們會針對不同蝕刻溫度及時間下對側壁蝕刻的速率深討其差異，最後以蝕刻溫度250oC、蝕刻時間為4分鐘為最佳參數。 最後我們把具有倒金字塔側壁結構應用在氮化鎵發光二極體元件製程上，再針對氮化鎵發光二極體進行光電特性分析，可以由量測結果發現，在同為注入電流350mA時，其傳統LED與IPS LED的Vf分別是3.90V與3.93V，其中IPS LED較高的Vf可能在酸蝕刻的過程造成LED P¬-GaN表面被破壞，而導致金屬電極與P型氮化鎵的歐姆接觸特性變差，所以才提高了串聯電阻值，但相較於傳統LED而言，IPS LED都具有較佳的光取出效率，光的輸出功率比傳統LED可以提升約8.9％。綜合以上內述，利用化學濕蝕刻技術形成IPS應用於氮化鎵發光二極體可有效提升發光二極體整體的光取出效率。 This research used chemical solution etching technique to create the inverted pyramid sidewall(IPS)structure which reduces the total internal reflection and increases the light scattering to improve the light extraction efficiency and then this inverted pyramid sidewall structure was applied on GaN LED. Then the LED photoelectrical characteristics and its effects on the light extraction efficiency of Light Emitting Diode are analyzed to see its effects on improving the performance of external quantum efficiency of LED. The epitaxy structures are grown on the sapphire substrate, and the surface of the LED is applied with PECVD (Plasma Enhanced Chemical Vapor Deposition) and coated with 2μm of SiO2 film as the mask for the mixed acid etching process, and then followed by the isolation process use Bonding Pad. It is necessary to use laser scribing to dice and expose the N face GaN. This allowed the heated etching fluid to etch the N face GaN and eventually become an inverted hexagonal pyramid sidewall structure on the sidewall of the LED. We also noted that the sidewall of the inverted hexagonal pyramid forms a 58o angle. In order to further verify the etching mechanism, we considered the effects of different temperature and time on the etching rate of the sidewall, and found the best results can be obtained when etching at 250oC for 4minutes. Finally we applied the inverted pyramid sidewall structure on the chip process of GaN LED, and then performed photoelectrical feature analysis on the GaN LED. We discovered that when 350mA current was applied, the Vf of Conventional LED and IPS LED are 3.90V and 3.93V respectively. The higher Vf of the IPS LED could be the consequence of acid etching process where the P-GaN surface of the LED was damaged, which resulted in the reduction of the ohm contact efficiency between the metal electrode and the p type GaN, thus increased the series resistance. However, when compared to the Conventional LED, IPS LED has better light extraction efficiency, which is approximately 8.9 % higher than Conventional LED. Summarizing the above, chemical etching technique forms IPS and when applied on GaN LED, it is able to effectively improve the light extraction efficiency.
