利用W-type量子井在磷化銦基板上實現中紅外光電激發雷射及波長可調外腔式雷射

Abstract

在本篇論文中，為了在磷化銦基板上解決延長發光波長和晶格匹配的問題，我們利用分子束磊晶(Molecular beam epitaxy)在磷化銦基板上成長六層以砷化銦鎵/銻砷化鎵W型量子井作為主動層的中紅外光雷射。藉由調整量子井的寬度以及成分比例，我們實現了2.1µm、2.2µm和2.33µm三種室溫操作之雷射，並加以分析及探討，其中波長為2.33µm的雷射內部量子效率 值為0.154，雷射的內部損耗 的值為17.9，且其雷射臨界電流密度Jth的值為0.6~0.8 kA/cm2相較於文獻紀錄大約低了2~3倍，此明顯的進步對於往後將波長延伸至2.5~3µm有莫大的幫助。 另外，對於實際雷射的應用，波長的可調性是非常重要的。我們利用外腔式的架構以達成可調波長之雷射。為了使波長可調制範圍更寬廣，我們將雷射鏡面鍍上一層抗反射膜來提高其臨界電流，其反射率小於3%，並使用Littrow外腔式架構，達到大範圍的波長調變 (2244nm到2376nm)，調變範圍高達132nm。

In this thesis, we report the fabrication and test result of mid-infrared semiconductor lasers on InP substrates. In order to extend the emission wavelength and solve the lattice mismatch problem, we used the W-type quantum wells based on type-II heterostructures. Emission wavelength up to 2.33μm and a record low threshold current was obtained at room temperature.

The active region consists of six periods of In0.66Ga0.34As / GaAs1-xSbx / In0.66Ga0.34As / GaAs0.6Sb0.4 W-type QWs. By optimizing the width and composition of the quantum wells, we demonstrated the 2.1μm, 2.2μm 2.33μm lasers operated at room temperature. By extraction, the internal quantum efficiency of the 2.33μm laser was 0.154, the internal loss was 17.9, and the threshold current density was about two to three times lower than the record in the literature. By further optimizing the device structure, we expect the lasing wavelength can be extend to 2.5 ~ 3μm in the near future. For practical application, the wavelength tunable mid-infrared laser is very useful. We used the external cavity setup with an antireflection (AR) coating on one side of the laser mirrors to study the tunability of our lasers. The Littrow external cavity setup was used and the tunning range up to 132nm (2244nm to 2376nm) at 11°C was obtained.