Photoluminescence at high pressures from highly strained MOVPE grown GaAs/GaSb/GaAs heterostructures

The authors report photoluminescence measurements made on highly strained nominally GaAs/GaSb/GaAs heterostructures (grown by MOVPE) at pressures up to 5.5 GPa in a diamond anvil cell. Two samples have been studied, a single 15 AA GaSb layer, and a five 15 AA GaSb layer heterostructure. In both cases the 1.3 eV strained layer luminescence increased in energy with pressure with a large pressure coefficient. This identifies the transition as one involving a Gamma state in the conduction band. It is suggested that lower energy luminescence, observed only from the five-layer sample, involves a defect. A theoretical model predicts that the bands line up in a type-II configuration, and the observed behaviour at pressures beyond the GaAs Gamma -X crossover confirms this. The possibility of incorporation of As atoms in the thin nominally GaSb layer is considered.