圖案化藍寶石基板氮化鎵系發光二極體之電雜訊量測及分析研究

Abstract

本論文研究氮化鎵銦發光二極體（InGaNLED）之低頻電雜訊特性與發光元件品質的關係；我們首先量測不同注入電流下之電雜訊頻譜，接著以經驗公式對個別頻譜作低頻的擬合分析，最後計算元件之雜訊指數並與LED品質作對應。實驗之LED樣品特別選取不同磊晶基板條件，分為三個部份來進行：（1）成長在平面藍寶石基板、圖案化藍寶石基板以及氮化鎵基板LED，（2）成長在一次與二次濕蝕刻之圖案化藍寶石基板LED，（3）成長在不同乾蝕刻高度之圖案化藍寶石基板LED；分析結果顯示品質較佳的LED，其雜訊指數亦較大。由於所萃取的雜訊指數代表雜訊強度對應電流的變化率，高品質的LED在低電流因此對應較低的雜訊振幅；我們同時透過材料與缺陷分析來驗證雜訊量測用於分析LED品質的可靠性。

In this thesis, the device quality of InGaN light-emitting diodes (LEDs) is investigated by studying their low-frequency noise characteristics. We firstly measurethe electrical noisespectra of LEDs under different current injection. Then the individual spectrum isfitted by empirical formula in low-frequency range. Finally the noise exponent is calculated and correlated to the LED quality. The LED samples grown on controlled substrates are intentionally selected for noise characterization, they are: (1) LEDs grown on flat sapphire substrate, patterned sapphire substrate (PSS) and GaN substrate, (2) LEDs grown on first and second wet-etched patterned sapphire substrate, (3) LEDs grown on dry-etched patterned sapphire substrate with different pattern height. Analysis has shown that high quality devices are associated with large noise exponent. Since the extracted noise exponent stand for theratio of noise intensity change to incremental current,high quality LEDs thereforepossesslower noise intensityunder low injected current. By the way, we have confirmed the LED quality by separate material and defect characterization.