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Theoretical study of optical properties of strained-layer heterostructures

In this presentation, the valence band mixing effect in strained quantum well structures based on the multiband effective mass theory is first presented. By using the envelope function approximation and the direct variation method, the valence band structures of some strained III-V semiconductor quantum well systems which are of interest to photonic applications are discussed. With the knowledge of the electronic wave functions and the energy band structures, optical gain behaviors of the strained quantum well systems are analyzed using the density matrix theory. The polarization dependence of the optical gain in strained layers is discussed in association with the dipole moment between the conduction band and the valence band. It is shown that biaxial compressive strain can reduce the asymmetry between conduction band and heavy-hole band masses, thus resulting in the reduction of laser threshold current as well as losses due to Auger recombination in semiconductor lasers.