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標題: InGaN-based Light-Emitting Diodes with Hexagonal Inverted Pyramid Structures through a Bandgap-selective Photoelectrochemical Process
利用選擇性光輔助電化學蝕刻技術製作 具倒立六角錐結構之氮化銦鎵發光元件
作者: Chien, Jui-Fen
關鍵字: 氮化銦鎵發光二極體;InGaN-based Light-Emitting Diodes;光輔助電化學;Photoelectrochemical
出版社: 材料科學與工程學系所
在本論文中,利用選擇性光輔助電化學濕式側向蝕刻技術,在元件平台區製作具有倒立六角錐之發光二極體並對此發光元件的光性與電性加以探討。本實驗將探討輕微側向蝕刻(Narrow Etching Width LED, NEW-LED),與延長側向蝕刻時間(Wider Etching Width LED, WEW-LED)兩者與傳統的發光二極體(Standard LED, ST-LED)的特性研究,文中將分別以提升取光效率與發光層應力釋放兩個主軸進行量測分析。實驗結論如下:(1)NEW-LED發光二極體元件達到最佳的亮度提升,其側向蝕刻寬度為內縮區寬度的1.5倍。(2)側向蝕刻確實可以降低多重量子井區的壓縮應力。(3) WEW-LED獨立倒立六角錐微結構中具有應力釋放效應,發光波長隨著注入電流增加,產生藍移的現象且半高寬變寬。
藉由量測WEW-LED的倒立六角錐結構的結果,計算其壓電場為-1.04MV/cm,相較於ST-LED(壓電場-1.66 MV/cm)有較小之壓電場效應,證實側向蝕刻可以達到多重量子井區的壓縮應力釋放。此外針對倒立六角錐微結構之顯微電激光譜量測,得知其發光波長與半高寬在平台中央、中間、邊緣的關係,波長藍移量分別是2.46nm、6.23nm、8.77nm,在具有倒六角錐的區域之光譜半高寬隨電流增加而變大,原因來自倒角錐中具不同尺度之量子盤結構發光。

Optical and electrical properties of InGaN-based light-emitting diodes (LED) with hexagonal inverted pyramid (HIP) structures on the mesa region were fabricated through a bandgap-selective photoelectrochemical (PEC) process that were performed in this thesis. An unintentionally doped GaN filter was uesd in the PEC etching process. During the bandgap-selective PEC lateral oxidizing and etching process, the narrow etching width from mesa edge to TCL edge was defined as a narrow etching width LED (NEW-LED), the etching width from mesa edge to TCL middle was defined as a wider etching width LED (WEW-LED) that was compared with standard LED (ST-LED) in subsequent. There were two aspects of this thesis. One was the enhancement the light extraction in LED structures, and the other was the compressive strain release of multiple quantum well (MQW). The conclutions were listed as three points: (1) The optimum lateral etching width of the NEW-LED was 1.5 times width of the TCL edge to mesa edge region that had the highest light extraction efficiency. (2) The LED with the lateral etching width structure had the partially compressive strain released property in the MQW active layer. (3) In an independent HIP structure of the WEW-LED, the wavelength blueshifed phenomenon and broad linewidth of EL spectra were observed by increasing the injection current.
After 30 minutes bandgap-selective PEC lateral etching process, the light intensities of the NEW-LED had a 44.5% enhancement at the frontside (0) and a 51.7% enhancement at the frontside (14.4) compared with ST-LED at 20mA. The superior enhancements of light extraction measured from the self-assembly HIP structures were attributed to the more paths to reduce total reflection between the p-GaN surface and air. Besides, a GaOx film was formed around the HIP structures after the electrochemical reaction that can suppress the leakage current.
We determined the piezoelectric fields of the WEW-LED through a photoluminesecence measurement by varying reverse electric fields. The piezoelectric fields in the WEW-LED (-1.04 MV/cm) was weaker than ST-LED (-1.66 MV/cm). The weaker piezoelectric fields were caused by the partially compressive strain release in InGaN active layer. By increasing the injection current, the wavelength blueshifted and the linewidth broadened properties of the WEW-LED were observed at the edge region with inverted pyramid structure structure.
Appears in Collections:材料科學與工程學系

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