Temperature dependence of the quantized states in aGaAs−Ga1−xAlxAssuperlattice

A detailed study of the photoreflectance spectra of a GaAs-${\mathrm{Al}}_{0.3}$ ${\mathrm{Ga}}_{0.7}$As superlattice as a function of temperature has revealed the temperature coefficients of the quantum-well transitions associated with the direct $\Gamma$ conduction band (CB) of GaAs and the staggered transitions from the $X-\mathrm{CB}$ of ${\mathrm{Al}}_x{\mathrm{Ga}}_{1-x}\mathrm{As}$ 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.