Pilot-Production Yield of Indium Phosphide-Based Thermophotovoltaic Monolithically Interconnected Modules

Yield data from a pilot-production run of thermophotovoltaic (TPV) devices are presented. A single lattice-mismatched 0.6 eV InGaAs epilayer device design was grown on 166 3-inch InP wafers by metalorganic vapor phase epitaxy (MOVPE) in a commercial reactor using standard chemical precursors. Epiwafers were processed in batch-style as 30-junction monolithically interconnected modules (MIMs) using standard proximity photolithography, wet chemical etching and plasma-enhanced chemical vapor deposition (PECVD). It is understood that yield is the product of several loss parameters. This work has shown that process consistency can be maintained and a reduction of losses at crystal growth can be achieved with the implementation of appropriate characterization techniques such as surfscan, photoreflectance, triple-axis X-ray diffraction (TAXRD) and in-situ temperature monitoring. In addition, InP as a substrate material has often been associated with an undesirably high incidence of wafer breakage. However, this work has shown that with some care in wafer handling, mechanical yield issues are not necessarily worse than in a standard GaAs fabrication line