Band structure and high-pressure measurements

Abstract

Determination of the electronic energy vs momentum relationship in semiconductors is essential for the prediction of almost all of their properties. In materials useful for mid-infrared applications, the simplest parabolic band approximations are usually insufficient. However relatively straight-forward numerical techniques based on the k.p method can yield good predictions for the bandstructure. The theoretical bandstructures can be compared with experiment using magneto-optics and magneto-transport, but one of the most useful tools for controllably tuning the system is hydrostatic stress. The strain modifies the bandstructure in a rather s imple way, principally by a linear increase in the fundamental gap, and thus it can be used to separate out effects that depend on bandgap. A large literature has built up on the study of near-infrared optoelectronic devices under pressure. These have been used to establish the variations of the radiative and non-radiative Auger recombination processes with band structure. The results predict that III-V mid-IR lasers with direct band gaps less than the spin-orbit gap should have threshold current densities less than the near-IR lasers based on InP or GaAs. These predictions are found to be consistent with the threshold current density and its variation with pressure observed in InGaAsSb/AlGaAsSb operating at 2.37μm at atmospheric pressure. Clearly high-pressure techniques provide exciting opportunities for the study of mid-infrared devices. © 2006 Springer-Verlag London Limited.