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GaInAsSb/GaSb and GaInAsSb/AlGaAsSb Heterostructures for TPV applications

Minority carrier lifetimes in 0.55-eV band-gap GaInAsSb epitaxial layers that are double capped with GaSb or AlGaAsSb layers were determined using time-resolved photoluminescence and modulation response to sinusoidal excitation. It was found that accumulation of electrons at the p-doped GaInAsSb/GaSb type-II interface contributes significantly to the interfacial recombination velocity (S), which was measured to be 3100 cm/s. The use of heavily p-doped GaSb cap layers was proposed to eliminate the potential well for electrons and barrier for holes at the interface. Increasing the GaSb cap doping level from 1 × 1016 cm-3 to 2 × 1018 cm-3 resulted in a 2.7 times reduction of S down to 1140 cm/s. The smallest value of S was determined to be 720 cm/s, which was obtained for structures with AlGaAsSb cap layers that have no valence band offset.