DIRECT DETERMINATION OF THE BAND DISCONTINUITIES IN INXGA1-XP/INYAL1-YP MULTIPLE-QUANTUM WELLS

The band structure. of In0.53Ga0.47P/In0.50Al0.50P 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+/-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 InxGa1-xP/InyAl1-yP 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 approximate to 18 meV/GPa, due to shifting of the heavy; and light-hole states with biaxial strain induced in the epilayers by applying pressure.