InGaAsSb/AlGaAsSb长波长多量子阱激光器有源区的优化设计

Optimal design of the active regions for InGaAsSb/AlGaAsSb long wavelength multi quantum well lasers

系统地研究了波长为 2 7μm的InGaAsSb AlGaAsSb多量子阱激光器中有源区的优化设计 .分别用含应变势的 6带KP模型和抛物带模型计算价带和导带的能带结构 ,并得到薛定谔方程和泊松方程的自洽解 ,由此计算量子阱在载流子注入时的增益谱 .研究表明制约量子阱增益的主要因素不是跃迁矩阵元 ,而是粒子数反转程度 ,尤其是空穴填充HH1子带的概率 .增加压应变或减小阱宽都会提高量子阱增益 .前者降低了价带HH1子带空穴的平面内有效质量 ;后者拉大了价带子带间距 ,尽管它同时略微增加了空穴有效质量 .这两种因素都导致价带顶空穴态密度的降低 ,提高了空穴在HH1子带的填充概率 ,最终提高了量子阱的增益 .所得结论与已有的实验报道相符 .

We present a theoretical study of the optical gain of InGaAsSb/AlGaAsSb type-I quantum well lasers, whose lasing wavelength is designed to be 2 7μm. A self-consistent solution, which solves the Schrdinger equations and Poisson equation simultaneously, is used to calculate the band structure and gain spectra of the quantum wells. By studying the influence of strain and width of the well material, we find that the main factor limiting the optical gain is not the optical matrix element, but the population inversion, especially the probability to find a hole in the first valence subband. Increasing the compressive strain or (and) decreasing the well width will enlarge the optical gain. The former lowers the in-plane effective mass of the hole. Although the latter slightly increases the in-plane effective mass of holes, it does enlarge the energy separation of the valence subbands. Both effects lower the total state density near the valence edge, and finally enlarge the optical gain. Our theoretical results can explain qualitatively the reported experimental results, and are useful for the design of InGaAsSb/AlGaAsSb long wavelength quantum well lasers.