Hetero-emitter GaP/Si Solar Cells with High Si Bulk Lifetime

III-V/silicon solar cells which have an active silicon bottom solar cell are promising for multi-junction solar cell applications. In such solar cell structures, a high minority carrier lifetime in the bulk silicon substrate is necessary. Annealing silicon wafers at high temperature (>= 500 degrees C) in the molecular beam epitaxy (MBE) high-vacuum chamber revealed significant lifetime degradation. In this work, we developed a practical method to maintain high Si bulk lifetime. SiNx layer deposited on Si back side helps maintain millisecond level minority carrier lifetime. By this procedure high minority carrier lifetime in the Si substrate is preserved while high quality thin GaP layer is achieved. We demonstrate GaP as a hetero-emitter layer with high Si bulk lifetime in GaP/Si structure solar cell with 524mV open circuit voltage.