Piezoreflectance study of a GaAs/Al_0.23Ga_0.77As asymmetric triangular quantum well heterostructure

We have studied the Piezoreflectance (PZR) spectra at 300 K, 80 K and 20 K related to the intersubband transitions from a GaAs/Al_0.23Ga_0.77As asymmetric triangular quantum well heterostructure fabricated by molecular beam epitaxy using the digital alloy compositional grading method. A comparison of the relative intensity of heavyand light-hole related features in the PZR spectra and those in the photoreflectance emphasizes the contribution of the strain dependence of the energies of the confined states, which allows us to identify unambiguously the features associated with the heavy- and light-hole valence bands. Comparison of the observed intersubband transitions with an envelope function calculation provided a self-consistent verification that the digital alloy composition grading method generated the desired effective linearly graded asymmetric triangular potential profile.