Characterization of GaAs solar cells made by ion implantation and rapid thermal annealing using selective photoetching

Abstract

Shallow n-p GaAs solar cells have been made by implantation of Si into Zn-doped (p-type) GaAs substrates followed by rapid thermal annealing. The structure of the GaAs crystal has been determined by the DSL photoetching method (Diluted Sirtl-like etchants used with Light). It was found that implantation-induced-damage (revealed by DSL as microroughness and craters) was not removed after annealing for energies exceeding 60 keV. This leads to substrates that contain many precipitates, which appears to be disastrous for the fabrication of good solar cells. In addition, good cell performance is hampered by compensation effects in the n-p transition region and in the n-type layer itself.