氧化侷限面射型雷射之二維(時間和空間)模擬分析

Abstract

本篇論文主要是以元件模擬分析的技術來探討弱折射率波導面射型雷射 (weakly index-guided VCSELs) 的特性。而根據氧化侷限面射型雷射 (oxide-confined VCSELs) 的物理特性和材料結構，我們可以建立一個三維的元件模型(其中有二維為空間向量，一維為時間向量)。藉由對載子密度速率方程式 (carrier rate equation) 和光子密度速率方程式 (photon rate equation) 的數值分析運算，並考量其熱效應、漏電流效應 (leakage current effect) 、電流散佈效應 (current spreading effect) 和載子擴散效應 (carrier diffusion effect) 而模擬出輸出功率的多模暫態響應、光-電流的特性曲線、光模態的競爭 (mode competition) 、空間燒洞 (spatial hole burning) 和小信號調變。

我們也發現當不考慮載子傳輸效應 (carrier transport effect) 時，電流散佈效應會比載子擴散在動態響應方面有較顯著的影響。在較低的電流散佈條件下，其可以得到較高的頻寬和較佳的低頻響應；推論其原因為較低的電流散佈將增加主動層中心區域 (core region) 的電流密度，因而具備較低的臨界電流 (threshold current) ，而呈現較佳的頻率響應特性。

面射型雷射的設計和製造是一項昂貴、耗時且需繁複製程步驟的工作。藉由本篇論文對模擬分析的研究，恰可提供一個準確又有效率的元件模型，進而縮短元件的設計週期並加速元件製程的發展。

The spatiotemporal simulation for weakly index-guided vertical-cavity surface-emitting lasers ( VCSELs ) are presented in this work. A three dimensional model (2 dimension in space domain and 1 dimension in time domain) is proposed based on physical and geometrical properties of oxide confined VCSELs. By solving carrier and photon rate equations numerically with thermal effect, current leakage effect, current spreading effect and carrier diffusion effect, we demonstrated the simulation capability including the multimode transient response of output power, light-current (LI) characteristics, optical mode competition, spatial hole burning (SHB), and small-signal modulation of VCSELs.

The influence of spreading current was found to be more dominative over carrier diffusion on dynamic response while the carrier transport is neglected. A higher bandwidth and better low frequency response are obtained under low current spreading condition that increases the current concentrated in the core region of the active layer results in low threshold current.

Design and fabrication of VCSELs, is expensive, time-consuming, and needs iterative process. This simulation tool provides an accurate and efficient device modeling, and can help on shortening the design cycle, and speed up the development process.