The Study on the Band Alignment and Characterization of GaAsSb/GaAs Quantum Well Lasers

本論文的主題為銻砷化鎵/砷化鎵量子井的能帶排列與特性的研究。此結構的能帶平移率在近十年來分別為許多不同的研究團體所提出，但卻一直無法達到共識。對此我們提出一個新穎的測定方式：我們成長一GaAs0.64Sb0.36/GaAs單量子井雷射二極體，利用雷射波長隨注入電流密度藍移的特性，比照自恰解模擬的結果，來擬合出價電帶平移率值。擬合所得的結果為 1.02 ，並得到 GaAsSb 的能隙彎曲參數為 -1.31 eV。在計算中我們亦發現，當載子濃度由低至高變化時，主導放光的躍遷將由高能階轉換至低能階，只有當載子濃度高至完全由低能階主導放光後，才會開始出現顯著的藍移效應。對於量子井雷射特性之模擬顯示，特徵溫度並非由自發性復合所主導；然而在應力承受許可的情況下，將 GaAs 位障層縮短會有助於增加電子電洞耦合量，因此可以降低起振電流密度，並改善特徵溫度。In the past decade, many research groups reported their valence band offset ratio (Qv0) for GaAsSb/GaAs system, but no common consensus is made yet. In this study, we propose a novel method to determine the valence band offset ratio by comparing the wavelength- cavity length relation of a GaAs0.64Sb0.36/GaAs single quantum well laser with a self-consistent solution. The determined valence band offset ratio and bowing parameter are Qv0 = 1.02 and bg = -1.31 eV respectively. In this calculation, we also found that when the carrier density is low, the dominant transition is from electron excited state to hole ground state. Only when the carrier density is high enough to form the band bending, electron ground state becomes the dominant transition level. Simulation results also show that spontaneous recombination does not dominate the characteristic temperature of our laser. A new quantum well structure with narrow GaAs barrier is analyzed. The simulation shows that the structure can enhance the coupling between electron and heavy hole wavefunctions. It may reduce the threshold current density, and further, improve the characteristic temperature, as long as the strain can be accommodated by the lattice.第一章 序論 .……………………………………………………… 1 1.1 雷射與光通訊簡介 .………………………………………………1 1.2 銻砷化鎵/砷化鎵量子井結構 .…………………………………… 5 第二章 元件製程與量測 ………………………………………12 2.1 雷射樣品磊晶成長 .………………………………………………12 2.2 寬面積邊射型雷射製程 .............…………………………………13 2.3 量測系統配置架構 .………………………………………………21 第三章 數值模擬方法 …………………………………………28 3.1 自恰解計算模型 .…………………………………………………29 3.2 多體效應 .…………………………………………………………32 3.3 量子井增益頻譜模擬計算 .………………………………………35 第四章 結果與討論 .……………………………………………50 4.1 GaAsSb/GaAs 能帶排列擬合結果 .………………………………50 4.2 GaAsSb/GaAs 量子井特性模擬 .…………………………………55 第五章 總結 .………………………………………………………79 參考文獻 ……………………………………………………………8