Abstract-In

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. 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 of electrons and barrier for holes at the interface. Increasing the GaSb cap doping level from 1ϫ10 16 to 2 ϫ10 18 cm Ϫ3 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.

No abstract

Auger recombination in p-type GaSb, InAs and their alloys is enhanced due to the proximity of the bandgap energy and the energy separation to the spin split-off valence band. This can affect the device performance even at moderate doping concentration. We report electron lifetime measurements in a p-type 0.54-eV GaInAsSb alloy, commonly used in a variety of infrared devices. We have studied a series of double-capped heterostructures with varied thicknesses and doping levels, grown by organometallic vapor phase epitaxy on GaSb substrates. The Auger coefficient value of 2.3 x lo-'* cm6/s is determined by analyzing the photoluminescence decay constants with a systematic separation of different recombination mechanisms.

Abstract. Thermophotovoltaic (TPV) diodes fabricated from 0.52eV lattice-matched InGaAsSb alloys are grown by Metal Organic Vapor Phase Epitaxy (MOVPE) on GaSb substrates. 4cm 2 multi-chip diode modules with front-surface spectral filters were tested in a vacuum cavity and attained measured efficiency and power density of 19% and 0.58 W/cm 2 respectively at operating at temperatures of T radiator = 950 °C and T diode = 27 °C. Device modeling and minority carrier lifetime measurements of double heterostructure lifetime specimens indicate that diode conversion efficiency is limited predominantly by interface recombination and photon energy loss to the GaSb substrate and back ohmic contact. Recent improvements to the diode include lattice-matched p-type AlGaAsSb passivating layers with interface recombination velocities less than 100 cm/s and new processing techniques enabling thinned substrates and back surface reflectors. Modeling predictions of these improvements to the diode architecture indicate that conversion efficiencies from 27-30% and ~0.85 W/cm 2 could be attained under the above operating temperatures.