Improving epitaxial regrowth interfaces as a means of improving doping superlattice solar cell performance

Steady improvements have been demonstrated in the fabrication process for GaAs doping superlattice solar cells, reaching a maximum efficiency of 9.0% for a non anti-reflection coated device under AM0 illumination. Numerous opportunities remain for improvement to reach a simulated one sun AM0 efficiency of 14.4%. Devices are fabricated by contacting the doping superlattice on the side-walls of the superlattice with either an n- or p-type GaAs regrown into an etched v-groove. The source of the dark current is believed to be traps at the interface between the regrown contact and the doping superlattice. The epitaxial regrowth process has been evaluated by modifying the etch process, cleaning processes and the epitaxial regrowth conditions with the objective of minimizing the interface trap density. An attempt to develop the best regrowth process conditions to reduce the interface trap density has been completed, however only a 1.6% relative increase was gained to an efficiency of 9.14%.