RADIATION RESPONSE OF HETEROEPITAXIAL N(+)P INP SI SOLAR-CELLS/

The effect of 1 MeV electron and 3 MeV proton irradiation on the perfo rmance of n(+) p InP solar cells grown heteroepitaxially on Si (PnP/Si ) substrates is presented, The radiation response of the cells was cha racterized by a comprehensive series of measurements of current versus voltage (I-V), capacitance versus voltage (C-V), quantum efficiency ( QE), and deep level transient spectroscopy (DLTS), The degradation of the photovoltaic response of the cells, measured under simulated 1 sun , AMO solar illumination, is analyzed in terms of displacement damage dose (D-d) which enables a characteristic degradation curve to be dete rmined, This curve is used to accurately predict measured cell, degrad ation under proton irradiation with energies from 4.5 down to 1 MeV. F rom the QE measurements, the base minority carrier diffusion length is determined asa function of particle fluence, and a diffusion length d amage coefficient is calculated, From the C-V measurements, the radiat ion-induced carrier removal rate in rile base region of the cells is d etermined, The DLTS data show the electron and proton irradiations to produce essentially the same defect spectra, and the spectra are essen tially the same as observed in irradiated homoepitaxial n(+) p InP. Fr om the DLTS data, the introduction rate of each defect level is determ ined. From the dark I-V curves, the effect of irradiation on the vario us contributions to the dark current are determined. The data are anal yzed, and a detailed description of the physical mechanisms for the ra diation response of these cells is given. The results enable a model t o be developed for the radiation response of the cells. (C) 1997 Ameri can Institute of Physics.