High-performance GaInAsSb thermophotovoltaic devices with an AlGaAsSb window

A large increase in the quantum efficiency (QE) and open-circuit voltage $V_{\mathrm{oc}}$ of GaInAsSb thermophotovoltaic (TPV) devices is obtained by the 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-μm-thick $n$ -GaInAsSb base layer, a 3-μm-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 $\text{>90\%,}$ compared with less than 60% for those without the window. At a short-circuit current density of $\text{∼1000\hspace{0.17em}}{\mathrm{mA/cm}}^{\mathrm{2}},$ $V_{\mathrm{oc}}$ of $\text{∼300\hspace{0.17em}}\mathrm{meV}$ 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 μm.