Direct determination of the band discontinuities in InxGa1-xP/InyAl1-yP multiple quantum wells.

Abstract

The band structure of ${\mathrm{In}}_{0.53}$${\mathrm{Ga}}_{0.47}$P/${\mathrm{In}}_{0.50}$${\mathrm{Al}}_{0.50}$P multiple quantum wells grown by molecular-beam epitaxy has been determined from pressure-dependent-photoluminescence measurements at low temperature. The photoluminescence signals from the direct-gap well and the indirect barrier were monitored as a function of pressure up to 4 GPa. High pressure transformed the multiple quantum well from a type I to a staggered aligned type II at 1.1 GPa. This transition was evidenced by the appearance of a photoluminescence signal due to the recombination of carriers separated in momentum and space. The simultaneous detection of this transition and that of the barrier material, allowed the direct determination of a valence-band offset energy of (0.24\ifmmode\pm\else\textpm\fi{}0.05) eV, without requiring any information on parameters of the bulk materials. Considering that the total band-gap discontinuity for this heterostructure system is 0.50 eV at 20 K, an approximate band-gap splitting of 52:48 is determined to be the band lineup at the InGaP/InAlP interface. Variations in the pressure coefficients of the indirect transitions in the barrier indicated that the valence band alignment changes with pressure at a rate of \ensuremath{\approxeq}18 meV/GPa, due to shifting of the heavy- and light-hole states with biaxial strain generated by applying pressure in the epilayers.