Carrier removal in lattice-mismatched InGaP solar cells under 1-MeV-electron irradiation

Radiation-induced majority carrier removal is investigated from n(+)/p(-) lattice-mismatched In0.56Ga0.44P solar cells under 1-MeV-electron irradiation. The change in carrier concentration in the 1x10(17) cm(-3)p(-) base layer is determined using standard capacitance-voltage techniques and found to proceed at a rate R-c=1.3 cm(-1), in agreement with that observed in lattice-matched InGaP. However, the observation of an increased short-circuit current and short-wavelength quantum efficiency over the unirradiated values at electron fluence levels in excess of 3x10(15) cm(-2), allows the carrier concentration from the n(+) emitter layer to be measured. By modeling the quantum efficiency of these solar cells, it is shown that the main photoresponse from these lattice-mismatched solar cells is due to drift transport, making the spectral response highly sensitive to changes in the width of the depletion region. Using this technique, the carrier concentration in the 2x10(18) cm(-3) n(+) emitter layer is found to be reduced to 1x10(18) cm(-3) after exposure to an electron fluence of 3x10(15) cm(-2). (C) American Institute of Physics.