n-type conduction in Ge-doped CuGaSe2

In order to prepare n-type CuGaSe2 as-grown, p-type CuGaSe2 single crystals were at first doped by Ge implantation. Thermal healing of the implantation damage in vacuum resulted in strong electrical compensation of the material, but not in n-type conduction. This limitation was overcome by annealing of implanted samples in Zn atmosphere, resulting in n-type conduction of CuGaSe2 with a carrier concentration at room temperature of up to 10(16) cm(-3). The samples were analyzed by photoluminescence, resistivity, and Hall effect measurements. It was found that the Zn-Ge codoping minimizes the formation of Cu vacancies, which act as acceptor levels and lead to self-compensation, by the formation of Zn-Cu defects. Furthermore, the number of electrically active Ge dopants is increased by a rise of the Ge-Ga concentration compared to the Ge-Cu defect density. The possibility of n-type conduction in Ga-rich CuIn1-xGaxSe2 compounds opens the possibility of the preparation of homojunction photovoltaic devices and might lead to improved solar cell performance of large band-gap chalcopyrites. (C) 1999 American Institute of Physics. [S0003-6951(99)02745-X].