Ion-assisted doping of CdTe

The possibility of using ion-assisted doping during growth of p-CdTe films for solar cells has been investigated, to obtain higher doping densities than previously obtained wtih conventional film deposition processes. For the first time, controlled doping has been demonstrated with low-energy phosphorus ions to obtain hole densities of up to 2 × 10¹⁷ cm^-3 in homo-epitaxial films deposited by vacuum evaporation on single-crystal CdTe. Solar cells made with these films suggest that ion damage reduces the diffusion length in the most highly doped films and that the active region of such cells must be made with considerably lower doping densities. For polycrystalline films on alumina, preliminary results indicate that the hole densities obtained are not sufficient to overcome grain boundary barrier limited conductivity.