具有高鋁成份薄位障層深紫外光氮化鋁鎵量子井的量測與分析研究

Abstract

在本論文中，我們先透過穿透式電子顯微鏡的觀察、X-射線繞射的倒晶格空間分布量測及 ω-2θ 掃描和幾何相位分析，初步判定三種不同深紫外光發光波長樣品內的量子井兩側存在高鋁含量障礙薄層。接著，經由穿透及光激螢光量測，特別是沿著樣品c軸方向施加壓力的光激螢光量測，我們瞭解樣品中高鋁含量層對能帶結構以及發光偏振行為的影響。我們也進行模擬研究獲得數值結果來和實驗數據比對。基本上，高鋁含量層對量子井層提供了c平面上額外的壓縮應變，讓重電洞能帶降低，且降低的幅度較分裂能帶者還大，造成重電洞能帶較分裂能帶低，因此導電帶與重電洞能帶間的電子躍遷能量較導電帶與分裂能帶間者小，發光偏振變成由垂直電場發光偏振主導。因此有此種高鋁含量障礙薄層的深紫外發光二極體之光萃取效率可以提高。

The material characterization techniques of transmission electron microscopy observation, reciprocal space mapping and ω-2θ scan in X-ray diffraction measurement, and geometric phase analysis are used for first identifying the existence of the high-aluminum layers (HALs) on both sides of a quantum well (QW) in three 3-period AlxGa1-xN/AlyGa1-yN (x < y) QW structures of different deep-ultraviolet (UV) emission wavelengths. Then, optical analyses, including transmission and photoluminescence (PL) measurements, particularly the PL measurements under an applied stress along the sample c-axis, are undertaken for understanding the effects of such HALs on the band structures and hence the polarized emission behaviors of the samples. Simulation studies are also performed for providing the favorable comparisons with the experimental data. Basically, the HALs produce an extra compressive strain in the c-plane for lowering the heavy-hole (HH) band edge (lower than the edge of the split-off band) such that the transverse-electric-polarized emission through the electron transition between the conduction and HH band becomes dominating. In this situation, the light extraction efficiency of such a deep-UV light-emitting diode can be enhanced.