Strain and Quantum Confinement Effects in Energy-Gap Reduction of Quantum Wells

We have discussed the energy-gap reduction due to exchange interaction and Coulomb correlation for quasi-two-dimensional In_xGa_1—xAs/InGaAsP quantum wells with variation of the well-width and the biaxial compressive strain as a function of the sheet density. The exchange-correlation self-energies have been calculated within the random-phase approximation, by solving a 4×4 Luttinger-Kohn Hamiltonian for the consideration of the valence-band nonparabolicity of the strained layer. We have found that the energy-gap reduction by the many-body effects grows with an increase of the biaxial compressive strain and the quantum confinement effect. At sheet density of n_s = 1×10¹² and 1×10¹³ cm^—2, our calculations show that for biaxial compressive strains of 0.47 to 1.02% and for well-widths of 40 to 20 Å the reduction ratios of the band-gap energy are about 3.9 to 4.6% and 3.1 to 4.26%, respectively.