Excitonic transition energies in strained InxGa1-xAs/In P and InxGa1-xAs/GaAs single quantum wells

Full text: In literature, a large amount of results for bound state energy levels in both conduction and valence band and excitonic transition energies for carriers confined in strained InxGa1-xAs=GaAs single quantum well (SQW) structures is available. In counterpart, there is a lack in similar results for strained InxGa1-xAs=In P QW results. This is because in the InGaAs/GaAs material system there is only compressive strain, whereas in the InxGa1-xAs=In P system compressive and tensile strains may be observed, depending on the In molar fraction. In this work, we investigate the dependence of the main exciton transition energies on the In molar fraction (via strain and barrier heights) and on the In segregation in both InGaAs/In P and InGaAs/GaAs SQWs. The exciton total energy was calculated as a sum of the following terms: electron and hole bound state energies, InGaAs bandgap energy, and the electron-hole pair binding energy (i.e. the energy related to the existing Coulomb attraction between electron and holes), taking into account well thicknesses within the so-called critical thickness regime. The computational model we build for solving the Schrodinger equation for the electron-hole pair is based on a variational approach, within the effective mass and envelope function approximations. We considered the quasi-2D excitons as being confined in an undoped strained quantum well with finite potential barrier heights, low temperature regime, and different dielectric constants along the growth direction. Both conduction and valence band offsets were determined experimentally for several values of In molar fractions (x). Our results were obtained analytically using MAPLE V software and they were compared to Tabun experimental data. The good agreement observed for both heavy-hole (HH) and light-hole (LH) excitons is emphasized. (author)