Deep level analysis of radiation-induced defects in Si crystals and solar cells

Deep level transient spectroscopy (DLTS) analysis of radiation-induced defe cts in p-type Si crystals and solar cells has been carried out to clarify t he mechanism of the anomalous degradation of Si n(+)-p-p(+) structure space cells induced by high-energy, high-fluence electron/proton irradiations. A large concentration of a minority-carrier trap with an activation energy o f about 0.18 eV has been observed in irradiated p-Si using DLTS measurement s, as well as the majority-carrier traps at around E-v+0.18 eV and E-v+0.36 eV, Correlations between DLTS data and solar-cell properties for irradiate d and annealed Si diodes and solar cells have shown that type conversion of p-Si base layer from p-type to n-type is found to be mainly caused by intr oduction of the 0.18 eV minority-carrier trap center, that is, this center acts as a deep-donor center. The E-v+0.36 eV majority-carrier trap center i s thought to also act as a recombination center that decreases minority-car rier lifetime (diffusion length). Moreover, origins of radiation-induced de fects in heavily irradiated p-Si and generation of deep-donor defect has al so been discussed. (C) 1999 American Institute of Physics. [S0021-8979(99)0 4813-6].