Hydrogen plasma passivation of GaAs on Si substrates for solar cell fabrication

The effects of hydrogen plasma treatment and postannealing on GaAs solar cells on Si substrates have been investigated. It is found that postannealing temperature is an important parameter to obtain GaAs on Si with a long minority carrier lifetime. The minority carrier lifetime is increased and the deep level concentration is decreased by the hydrogen plasma treatment. Even after 450°C postannealing with the complete recovery of the shallow impurity level, the minority carrier lifetime is still longer and the deep level concentration is lower than those of the as-grown sample. It means that the defects in GaAs on Si are passivated by hydrogen. The efficiency of GaAs-on-Si solar cell (air mass 0, 1 sun) is improved from 16.6% (as-grown) to 18.3% by the hydrogen plasma passivation and to 17.2% by the hydrogen plasma passivation and postannealing at 450°C