表面淺層蝕刻與鋅擴散的離子佈植型面射型雷射之製造與分析

Abstract

本論文主要探討表面蝕刻及和鋅擴散對 850 nm 離子佈植面射型雷射單模表現的影響。我們推導Laguerre-Gaussian 模及線性偏振模的光場強度於空間位置上的分佈，並分析溫度對橫模光點尺寸的影響。在調節布拉格反射鏡的反射率方面，我們模擬計算表面蝕刻對原有的850 nm分散型布拉格反射率的影響，得到86 nm的蝕刻深度，可得到的最小反射率值0.985，此結果與我們實作的實驗數據相吻合。在布拉格反射鏡的表面進行鋅擴散的模擬計算上，我們得到隨著擴散的時間增加，反射率下降且止帶間距縮小，而對原有反射率近乎1.0的850 nm分散型布拉格結構言，我們得到了在溫度600 ℃ 下通行8至16分鐘的鋅擴散時間可將分散型布拉格反射鏡的反射率改變為0.95。將上述的兩種表面修正反射率的方法應用於製作單一橫模的面射型雷射，由於離子佈植製程造成元件的串聯電阻過大，使得大部分元件無法發光。其它發光的元件上我們量測L-I發現僅有發光二極體的特性，導致此原因可能是因為表面反射率下降造成元件的臨界增益增加，因此，不容易產生雷射光。

In this study, we fabricated and analyzed the 850 nm ion-implanted vertical-cavity surface emitting lasers (VCSELs) with shallow-etching and zinc-diffusion onto the surface distributed Bragg reflector (DBR). The Laguerre-Gaussian modes and linear polarization modes were applied for determining mode intensity distribution. The temperature effect on the mode spot size was evaluated. We calculated the reflectance of shallow-etched and zinc-diffused 850 nm DBR. We found that there is a local reflectance minimum of 0.985 with surface etching depth of 86 nm. This calculation is coincident to our experimental result. For the case of zinc diffusion, we found that the reflectance and stop band decrease with the diffusion time. The resultant DBR reflectance is about 0.95 with for the diffusion time of 8 ~ 16 minutes at 600 ℃. Due to an amorphous film formed over the DBR surface, the measured reflectance is much lower than the simulated result and is not comparable to the simulation result. We applied separately the shallow-etching and zinc-diffusion techniques to fabricate single mode 850 nm ion-implanted VCSELs. Due to a large series resistance of VCSELs resulted from the small ion-implanted aperture size, most devices cannot reach the threshold lasing condition. The measured relationship of light power to current indicates the characteristics of light emitting diodes. By adequately controlling the aperture sizes of ion-implantation and surface relief or zinc diffusion, the feasible single-mode VCSELs are suggested to be fabricated successfully.