Failure analysis of heavily proton irradiated p+-n InGaP solar cells by EBIC and cathodoluminescence

In this paper the effects of heavy proton irradiation on single-junction (SJ) p+-n InGaP solar cells are investigated by means of electron-beam-induced-current (EBIC) and cathodoluminescence (CL). A hole diffusion length reduction from 0.3 to 0.02 μm after 1×1014 protons/cm2 irradiation is estimated from EBIC measurements. Such degradation is attributed mainly to IE3 point defects as evidenced by the temperature dependence of the CL intensity. The electronic activity of such defects is shown to be reduced after thermal treatment. Indeed an enhancement of the light emission is observed after electron bombardment only on InGaP while no recovery is observed on the GaAs substrate. Such results illustrate the potential of EBIC/CL in device failure analysis as they are non-destructive techniques.