Laser emission in CdHgTe in the 2-3.5 µm range

Stimulated emission from HgCdTe separate confinement heterostructure waveguides embedding quantum wells as gain medium is studied. We explore the effect of composition grading in the barriers as well as that of using strained quantum wells on the temperature evolution of the laser threshold. The main effect of barrier grading is to suppress carrier trapping at low temperatures, leading to an improved excitation transfer from the barriers to the quantum wells, and to an intrinsic exponential dependence of the threshold on the temperature. For the strained quantum well structures, a two-fold reduction of the threshold is obtained, as compared with similar band gap unstrained structures. The threshold dependence on photon energy points out the importance of Auger type nonradiative recombinations. We determine the Auger constant in our structures, and compare them with published data. An exponential dependence of the Auger constants on the band gap, valid for type I heterostructures, is shown. A comparison of the published operating temperatures in competing devices is done. It appears that III–V type II and unipolar lasers are largely ahead of II–VI lasers. The future of HgCdTe could lie in vertical cavity, surface emitting lasers