High-efficiency carrier collection and stimulated emission in thin (50 Å) pseudomorphic In<i>x</i>Ga1−<i>x</i>As quantum wells

Abstract

Efficient collection of photoexcited electrons and holes by thin, strained quantum wells is demonstrated in an In0.16Ga0.84As-GaAs pseudomorphic quantum well heterostructure laser. The undoped laser structure, which was grown by molecular beam epitaxy, consists of five 50 Å pseudomorphic In0.16Ga0.84As quantum wells separated by thick (700 Å), unstrained GaAs confining layers. Despite the fact that the quantum wells are undoped, decoupled, and of dimensions which are known to be too small to provide efficient carrier collection in unstrained AlxGa1−xAs-GaAs structures, 77 K photopumped laser operation is achieved on quantum well transitions (λ∼870 nm) at a threshold excitation intensity of 9.3×103 W/cm2. At photoexcitation intensities even as high as five times the threshold value, spontaneous emission from the quantum well is more than 700 times as intense as the confining layer luminescence. Based upon these photoluminescence results and some simple physical arguments, we suggest that carrier collection is enhanced in pseudomorphic quantum wells.