A large increase in the quantum efficiency (QE) and open-circuit voltage V-oc of GaInAsSb thermophotovoltaic (TPV) devices is obtained by thr use of an AlGaAsSb window layer compared with devices without a window layer. The TPV structure, grown on GaSb substrates by organometallic vapor phase epitaxy or molecular beam epitaxy, consists of a 1-mu m-thick n-GaInAsSb base layer, a 3-mu m-thick p-GaInAsSb emitter layer, a 100-nm-thick AlGaAsSb window layer, and a 25-nm-thick GaSb contacting layer, The band-gap energy of the lattice-matched GaInAsSb is 0.53-0.55 eV. The peak internal QE of the TPV cells with the window is > 90%, compared with less than 60% for those without the window. At a short-circuit current density of similar to 1000 mA/cm(2), V-oc of similar to 300 meV is obtained for cells with the window layer, compared with less than 220 meV without the window layer. These increases are attributed to a substantial decrease in the surface recombination velocity with the window layer. Based on a standard calculation, the electron diffusion length in the p-GaInAsSb layer is at least 5 mu m. (C) 1997 American Institute of Physics. [S0003-6951(97)03252-X].
