Demonstration of nitride-on-phosphide hybrid tandem solar cells by using surface-activated bonding

Group-III nitride-on-phosphide hybrid tandem solar cells were fabricated using surface-activated bonding. The bottom surface of nitride top cells grown on GaN substrates was bonded on the top surface of InGaP-based bottom cells grown on n-GaAs substrates. Their tandem-cell operation was successfully demonstrated by confirming that the open-circuit voltage (V_OC) of tandem cells was enhanced. It was also found that the electrical properties of the bonding interface do not induce fatal effects on the performance of the tandem cells.