Recent progress in InGaAsSb/GaSb TPV devices

AstroPower is developing InGaAsSb thermophotovoltaic (TPV) devices. This photovoltaic cell is a two-layer epitaxial InGaAsSb structure formed by liquid-phase epitaxy on a GaSb substrate. The (direct) bandgap of the In/sub 1-x/Ga/sub x/As/sub 1-y/Sb/sub y/ alloy is 0.50 to 0.55 eV, depending on its exact alloy composition (x,y), and is closely lattice-matched to the GaSb substrate. Internal quantum efficiencies as high as 95% have been measured at a wavelength of 2 microns. At a wavelength of 1 micron, internal quantum efficiencies of 55% have been observed. At a current density of 1.6 A/cm/sup 2/, an open-circuit voltage of 0.250 V and a fill factor of 60% have been measured. Our results to date show that the GaSb-based quaternary compounds provide a viable and high performance energy conversion solution for thermophotovoltaic systems operating with 1000 to 1500/spl deg/C source temperatures.