PIEZOREFLECTANCE STUDY OF A GAAS AL0.23GA0.77AS ASYMMETRIC TRIANGULARQUANTUM-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/Al0.23Ga0.77A s asymmetric triangular quantum well heterostructure fabricated by mol ecular beam epitaxy using the digital alloy compositional grading meth od. A comparison of the relative intensity of heavy- and light-hole re lated features in the PZR spectra and those in the photoreflectance em phasizes the contribution of the strain dependence of the energies of the confined states, which allows us to identify unambiguously the fea tures associated with the heavy- and light-hole valence bands. Compari son 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 linea rly graded asymmetric triangular potential profile.