0.6-eV bandgap In0.69Ga0.31As thermophotovoltaic devices with compositionally undulating step-graded InAsyP1−ybuffers

Abstract

Single-junction, lattice-mismatched In0.69Ga0.31As thermophotovoltaic (TPV) devices each with abandgap of 0.6 eV are grown on InP substrate by metal—organic chemical vapour deposition (MOCVD). Compositionally undulating step-graded InAsyP1−y buffer layers with a lattice mismatch of ∼1.2% are used to mitigate the effect of lattice mismatch between the device layers and the InP substrate. With an optimized buffer thickness, the In0.69Ga0.31As active layers grown on the buffer display a high crystal quality with no measurable tetragonal distortion. High-performance single-junction devices are demonstrated, with an open-circuit voltage of 0.215 V and a photovoltaic conversion efficiency of 6.9% at a short-circuit current density of 47.6 mA/cm2, which are measured underthe standard solar simulator of air mass 1.5-global (AM 1.5 G).