半極性氮化銦鎵/氮化鎵量子井在應力控制下之發光特性以及雙色發光二極體之載子傳輸研究

Abstract

在本篇論文中，我們有系統的研究了以氮化鎵為材料的發光二極體在兩個方面，分別是半極性氮化銦鎵/氮化鎵量子井在應力控制下之發光特性以及雙色發光二極體之載子傳輸之研究。 論文的第一部份我們探討了(11$ ar{2}$2)和(20$ ar{2}$1)長晶方向之半極性氮化銦鎵/氮化鎵單一量子井發光二極體的光學非等向性，並深入討論不同濃度的銦以及沿著'c'軸投影方向上不同程度的應力釋放所造成的影響。 我們利用我們實驗室發展的一維模型去求解漂移擴散、帕松以及 6$ imes$6 $k cdot p$ 薛丁格方程來分析能帶結構圖和發光特性。 研究顯示對於(11$ ar{2}$2)長晶方向的發光二極體而言，我們可以發現一個隨著銦濃度增加而發生發光極化方向改變之現象。 對於(20$ ar{2}$1)長晶方向的發光二極體而言，隨著銦濃度的增加加上一定程度上的應力釋放，其極化率可以被提升至超過90$\%$，這對於雷射及液晶顯示器背光模組的應用上有著極大的潛力。 論文的第二部份我們探討了一種創新結構的雙色發光二極體之載子傳輸研究，這種創新的結構是在兩組不同波長之多層量子井之間插入了一層摻雜電洞之氮化鎵。 這裡我們利用了二維模型去求解漂移擴散以及帕松方程，並額外加上一個考慮銦濃度波動之外掛函數來使我們的模擬結果更加準確。 結果顯示適度的選擇在摻雜電洞之氮化鎵插入層的摻雜濃度和厚度，即使在低電流密度下，我們仍然可以有效的優化兩種波長的輸出光強度之間的比例。

In this thesis, we systematically study the GaN-based LEDs in two aspects: the emission characteristics of semipolar InGaN/GaN quantum well with strain manipulation and the carrier transport of dual color light-emitting-diodes. The first part of the thesis investigates the optical anisotropic behaviour of the (11$ ar{2}$2) and (20$ ar{2}$1) semipolar InGaN/GaN single quantum well LEDs. The influence of different indium compositions of the quantum well, and different degrees of strain relaxation along the projection of $c$-axis are discussed in detail. Our developed one dimensional model is used to solve drift-diffusion, Poisson equations, and 6$ imes$6 $kcdot p$ Schr'{o}dinger equations to investigate the band structures and emission characteristics. The study shows that for the (11$ ar{2}$2)-plane, there exists a switching of light emission polarization directions with the increase of indium composition. While for the (20$ ar{2}$1)-plane, the polarization ratio $ ho_{y'x'}$ can be achieved over 90$\%$ with a high indium composition and a large degree of strain relaxation, which is promising for laser diodes and LCD backlight modules applications. The second part of the thesis will investigate the carrier transport of a novel GaN-based dual color light-emitting diodes (LEDs) with an additional p-GaN layer inserted between the two-color wavelength MQWs. We apply our 2D Poisson, drift-diffusion solver with an extra plug-in function considering the indium fluctuation to make the simulation result more precise. The result shows that by properly selecting the doping density and the thickness of the p-GaN insertion layer, we can effectively optimize the ratio of output light intensities between the dual color wavelength even under a low bias current density.