量子井面向雷射特性與數值模擬

Abstract

近年來，面向雷射由於具有一些較傳統半導體雷射優異特性，引起廣泛探 討。為了深入了解面向雷射特性並決定最佳之元件結構，一個適當的元件 模擬器是迫切需要的。在本論文中，我們發展了一套適用於面向雷射的二 維數值模擬，整個模擬是建立在自我一致的架構上。在電的方面所包含的 物理模式有波松方程式、電流連續方程式，而為了準確的計算量子井內的 增益，我們必須引進薛丁格方程式來描述量子效應。在光的部分，其中的 物理模式有耦合模式方程式以及光子數目的增益方程式。經由將描述光和 電特性的模式整合為一體，我們可模擬出在穩態時面向雷射的光和電特性 。從模擬中我們可獲得面向雷射電流與雷射光強度的關係曲線、能帶圖、 電子電洞濃度及光的分佈。除此之外，對於量子井內之次能帶與載子波函 數等量子效應亦可由模擬中獲得。在此模擬中，我們改變了面向雷射反射 鏡對的數目、增益層的厚度以及孔徑大小來探討元件結構對雷射性能的影 響。結果顯示當反射鏡對數為17、增益層厚度約在295埃至 320埃以及孔 徑直徑在6um至10um間時，面向雷射性能為最佳。對於面向雷射的研究， 此模擬結果可做為元件設計的參考並提供改進的方向。 In the past few years, there has been an increasing interest in the realization of vertical-cavity surface-emitting lasers (VCSEL's). This is mainly due to the attractive features of these devices such as on-wafer testing, and high-density 2D arrays. To study the characteristics of these devices and to determine the optimal device structure, a numerical simulator for VCSEL's necessary. In this thesis, we develop a two- dimensional for VCSEL's. The physical model includes the Poisson equation, continuity equation, Schrodinger equation, coupled-mode equation and photon rate equation. The result we obtain from the simulation is the laser output power versus current, band diagram, carrier concentration and optical wave distributions. In addition, quantum-size-effects such as the subband energies and the overlap integral for optical transitions can be derived from the simulation. We also change the device structure of VCSEL's such as the number of mirror thickness of active layer and cavity size to investigate the geometrical effect on the laser performance. The results of are used as guidelines for VCSEL structure design and