Nonparabolicity effects on carrier lifetimes in bulk Hg_(1-x)Cd_xTe alloys and Mid-Infrared 2D Hg_(1-x)Cd_xTe/CdTe Single Quantum Well Lasers

摘要

We report on a theoretical study of nonparabolicity (NP) effects on carrier lifetimes in narrow energy bandgap bulk (3D) Hg_(1-x)Cd_xTe ternary alloys and their related 2D Hg_(1-x)Cd_xTe/CdTe Single Quantum Well (SQW) nanostructures for Mid-infrared (MIR) Laser applications. Carrier lifetime (τ) calculations are performed within both the parabolic and the 4-band CB + HH + LH + SO nonparabolic models. We show that NP affects strongly all three main scattering processes: Auger, Schockley-Read-Hall (SRH), and radiative recombination (RR). At 300 K and in mid-Cd contents (0.4 < x < 0.6) 3D Hg_(1-x)Cd_xTe alloys, Auger 1 is shown to be the dominant τ limiting factor. In 2D Hg_(1-x)Cd_xTe/CdTe SQW nanostructures, we show that RR turns out to be the dominant τ limiting process. This strongly reduced influence of Augerl process in 2D Hg_(1-x)Cd_xTe/CdTe SQW nanostructures is the result of the strong 2D quantum confinement induced amplification of NP effects via much stronger electron (CB) and all three hole (HH, LH, SO) energy subbands interactions and mixing. As a consequence, NP effects are finally shown to significantly improve all main 2D Hg_(1-x)Cd_xTe/CdTe SQW Laser parameters in the MIR λ range with an optimum at x = 0.45 and for wide enough QW with L_z ≥ 100 A.