Characterization of GaInP/Ge heterostructure solar cells by capacitance measurements at forward bias under illumination

Abstract

The n-GaInP/n-p Ge heterostructure sloar cells grown by OMVPE were studied by new technique based on the diffusion capacitance measurements under illumination at open circuit voltage conditions. The value of the effective minority carrier lifetime in the p-Ge base τeff= 1.5×10 -6 s was determined from the frequency dependence of the diffusion capacitance, C(f). The numerical simulation model was developed, which is in a good agreement with the experimental C(f), capacitance-voltage and dark current-voltage measurements. The value of the bulk minority lifetime equal to τ b= 5×10 -6 s was obtained by the simulation fit of the experimental data. The simulations have also demonstrated that the diffusion capacitance is very sensitive to the recombination velocity at the back contact, Sbc, for Sbc<10 5