High Performance 2.5 Micron InGaAs/InP TPV Cells Based on Novel Buffer Technology

Due to a mature material growth and processing technology of InP and InGaAs, lattice-mismatched 2.5 um(0.55 ev )InGaAs/InP is identified as the most promising Thermophotovoltaic(TPV) material system for the next generation of monolithic interconnected modules(MIMs). Compared to GaSb and quaternary InGaAsSb, InP and InGaAs offer many critical advantages; (l)the existence of semi-insulating InP substrate enabling MIMs development(GaSb does not have semi-insulating form), and (2)proven high temperature reliability of InGaAs. The reliability of the meta-stable quaternaly InGaAsSb at high TPV operating environment is a concern, due to a large miscibility gap, and the ability to use InGaAsSb/GaSb materials in the MIMs is not proven yet. However, the performance of 0.55 ev InGaAs/InP TPV cell is still inferior than dislocation free 0.74 ev lattice-matched InGaAs/lnP cell due to the high density of mismatch generated threading dislocations. ELI proposes a novel approach to incorporate a new composition graded buffer layer (CGBL) to reduce/eliminate the threading dislocation and dramatically improve the performance of 0.55 ev InGaAs/InP TPV cells and MIMs. In phase I, design and growth of the novel buffers will be carried out, and improved TPV will be demonstrated. The optimization of CGBL and high performance TPV will be realized in phase II.