氧化鋁薄膜應用於氮化鎵光電元件之研究

Abstract

由於傳統製程氧化鋁薄膜之方法，需真空環境與花費較高的製程成本。因此為了解決此問題，本論文運用有機鋁溶液於氧氣環境中經高溫爐管退火之方式來製程AlxOy薄膜。進而將所測試之AlxOy薄膜應用於三種氮化鎵光電元件上，分別為發光二極體、紫外光檢測器與光電化學電池。 本論文首先將AlxOy薄膜應用於發光二極體之側壁鈍化層，綜合電性與光性之結果，我們成功的將其應用於Ni/Au透明導電層之發光二極體。但由於AlxOy薄膜製程環境嚴重耗損ITO薄膜之電特性，因此AlxOy薄膜應用於ITO透明導電層之發光二極體上並無較佳之效果。接著我們將此AlxOy薄膜應用於光檢測器之氧化層，相較於傳統二氧化矽光檢測器，AlxOy光檢測器確實能夠有效降低元件之漏電流，並獲得較佳之可見光鑑別率。最後我們將其應用於光電化學電池之保護層，我們為了求得試片較佳之產氫效率，因而設計兩大部分來改善此元件。分別為改變磊晶結構使試片具有二維電子氣之功能與在試片背面加入Al反射層。但由於試片長久浸泡於電解液溶液中，背部反射層會與電解液反應產生剝落之現象，因此我們運用此AlxOy來保護試片背部之反射層。最終我們成功的提升試片之光電流密度。

Traditional fabrication of aluminum oxide (AlxOy) thin film requires a vacuum system and also incurs higher process costs. To help alleviate these constraints, this study explores the use of an organic aluminum solution to fabricate AlxOy thin film through thermal annealing in oxygen ambient at atmospheric pressure. After fabrication, sample AlxOy thin films were applied to three gallium nitride (GaN) optoelectronic devices: a light emitting diode (LED), an ultraviolet (UV) photodetector (PD), and a photoelectrochemical cell. First, we applied AlxOy thin film to an LED with a passivated sidewall. According to electrical and optical results, the AlxOy thin film successfully adhered to the LED with Ni/Au transparent conductive layer (TCL). However, the O2 ambient of the AlxOy thin film severely decreased the conductivity of the indium tin oxide (ITO) thin film. Therefore, no significant improvement was realized from applying the AlxOy thin film to the LED with ITO TCL. Next, we applied AlxOy thin film to the gate layer of a PD. The PD with AlxOy gate layer was minimized leakage current more effectively than a typical PD with SiO2 gate layer, thus promoting better visible light detection. Finally, we applied the AlxOy thin film onto the protective layer of a photoelectrochemical cell. To obtain better hydrogen production efficiency, two modifications were made to improve this device performance. The epitaxial structure was altered to give the sample a two dimensional electron gas (2DEG) structure. Additionally, an A1 reflective layer was inserted behind the sample. However, prolonged soaking of the sample in electrolytic solution led to peeling off of the reflective layer due to a reaction between the layer and the electrolytic solution. Therefore, we applied AlxOy thin film to protect the reflective layer on the back of the sample and successfully enhanced the hydrogen production efficiency of the sample.