Modeling and analysis of photomodulated reflectance and double crystal x-ray diffraction measurements of tensilely strained InGaAs/InGaAsP quantum well structures

Abstract

Room temperature photomodulated reflectance (PR) and double crystal x-ray diffraction (DCXRD) measurements have been performed on a series of tensilely strained InxGa1−xAs multiple quantum well (QW) laser structures, with In0.80Ga0.20As0.43P0.57 barriers, which are lattice-matched to an InP substrate. Seven samples are studied, with nominal QW In composition varying between x=0.533 and 0.316, corresponding to biaxial tensile strains between 0% and 1.5%, respectively. The DCXRD measurements provide accurate information on composition, strain and layer thickness, while the PR yields the energies of both allowed and forbidden critical point interband QW transitions, and how these vary with strain, particularly the transitions between the ground-state conduction band and heavy/light hole valence band levels. A three-band effective mass formalism is used to model the QW transitions and very good agreement with the PR measurements is obtained once excitonic binding energies, and the quantum confined Stark effect are taken into account.