Monolithic Series‐Interconnected GaInAsSb/AlGaAsSb Thermophotovoltaic Devices Wafer Bonded to GaAs

GaInAsSb/AlGaAsSb/GaSb epitaxial layers were wafer bonded to semi‐insulating GaAs wafers for monolithic series interconnection of thermophotovoltaic (TPV) devices. SiOx/Ti/Au was used as a bonding layer to provide electrical isolation and to serve as an internal back‐surface reflector (BSR). The minority‐carrier lifetime in WB BSR structures is more than two times longer than that of control structures without a BSR. WB GaInAsSb/AlGaAsSb TPV cells were fabricated and monolithically interconnected in series. These cells exhibit nearly linear voltage building. At a short‐circuit current density of 0.4 A/cm2, Voc of a single TPV cell is 0.2 V, compared to 0.37 and 1.8 V for 2‐ and 10‐junction series‐interconnected TPV cells, respectively.