氮化鎵面射型雷射之設計與模擬

Abstract

氮化鎵面射型雷射在光影像及儲存系統有著非常廣大的應用性，如全彩顯示器及高密度光儲存系統等等。而布拉格反射鏡扮演提供面射型雷射結構中極高反射鏡的重要組成。我們設計氮化鎵面射型雷射結構以及適合此波域的布拉格反射鏡結構，並製造了40對GaN/AlGaN 布拉格反射鏡結構和極高反射率的氧化物DBR結構。 為了模擬這些結構的特性，我們利用transfer matrix method計算面射型雷射和布拉格反射鏡的反射頻譜，以及對常溫、脈衝操作的面射型雷射的臨界電流密度做詳細的分析。 我們設計並製造40對的GaN/AlGaN DBR結構，其反射率為88.2％；利用TiO2， ZrO2 ，HfO2 和SiO2…等氧化物材料製造的DBR結構，其反射率高達99.99％，且樣品的表面平整度為1/150中心波長。

GaN-based vertical cavity surface emitting laser (VCSEL) is an important device for optical imaging systems such as full-color display panels, high-density optical recording and photolithography. Distributed Bragg reflector (DBR), a high reflectance mirror structure, is one key of part for achieving laser operation for GaN-based VCSELs. We designed GaN-based VCSEL and DBR structure and fabricated the dielectric DBRs and a 40-pair GaN/AlGaN multilayer of DBR. To simulate the properties of these structures, we use transfer matrix method to calculate the reflectance spectrum of DBRs and VCSELs. A detailed threshold analysis of room temperature pulsed operation of GaN-based VCSEL is also carried out, the structure has DBR with Al composition of 0.35 as the top and bottom mirror and the five pair InGaN quantum wells with In composition of 0.15. To fabricated the real DBR structures, we used three high index materials including TiO2, ZrO2 and HfO2 combined with SiO2 as low index material to fabricate the dielectric DBR structure. Three reflector structures are fabricated on various substrates and obtained high reflectivity up to 99% with good surface morphology of 1/150 center λroughness. We also fabricated GaN/AlGaN multiplayer DBR and obtain a reflectance of 90% at a center wavelength of 442 nm using the Al composition of 0.34.