High-pressure studies of GaAs-Ga1-xAlxAs quantum wells of widths 26 to 150 Å

URL:http://link.aps.org/doi/10.1103/PhysRevB.33.8416 ; DOI:10.1103/PhysRevB.33.8416Photoluminescence spectra of GaAs quantum wells of widths 26 to 150 Å are studied as a function of hydrostatic pressure (0-70 kbar) at 80 and 150 K. The pressure coefficients of both the heavy- and light-hole excitons are found to decrease with decreasing well width. The direct to indirect conduction-band crossover, leading to the formation of type-II heterostructures, occurs at higher pressures for wider wells. A transition associated with the X conduction band in quantum-well structures is observed and its pressure dependence is established. Correlating this transition to barrier-to-well recombination determines the valence-band offset.The work at the University of Missouri was supported by Amoco Corporation and the Research Corporation (New York, NY). M.C. also thanks the Alfred P. Sloan Foundation for support

Temperature dependence of the quantized states in a GaAs-Ga1-xAlxAs superlattice

URL:http://link.aps.org/doi/10.1103/PhysRevB.37.1035 DOI:10.1103/PhysRevB.37.1035A detailed study of the photoreflectance spectra of a GaAs-Al0.3Ga0.7As superlattice as a function of temperature has revealed the temperature coefficients of the quantum- well transitions associated with the direct Γ conduction band (CB) of GaAs and the staggered transitions from the X-CB of AlxGa1-xAs to the valence band of GaAs. The data have been fitted to Varshni's equation. We have also observed the evolution of the excitonic transitions, especially for lower quantized states, as the temperature is decreased yielding the binding energies.This work ws supported by the u.S. Department of Energy under Contract No. DE-AC0284ER45048. The work by one of us (M.C.) was supported in part by the Alfred P. Sloan Foundation

High-pressure studies of GaAs-AlxGa1-xAs quantum wells at 300 and 80 K using photoreflectance spectroscopy

URL:http://link.aps.org/doi/10.1103/PhysRevB.38.9790 DOI:10.1103/PhysRevB.38.9790A detailed photoreflectance study of a GaAs-Al0.3Ga0.7As multiple quantum well of well width 260 Å is carried out at 300 and 80 K. The pressure dependence of a large number of quantized states is observed. The sublinearity of pressure dependence increases with increasing quantum number. A model calculation that includes the pressure dependence of electron effective mass accurately describes the data. Transitions associated with L and X band extrema are observed and their pressure coefficients deduced.This work was supported by the U.S. Department of Energy under Contract No. DE-AC02-84ER45048 and by the U.S. Army under Contract No. DAAL03-86-K0083