Noise Properties ofn-Type Gold-Doped Silicon

Measurements are reported of noise in $n$-type gold-doped silicon at reduced temperatures, both in thermal equilibrium and under optical illumination. The noise level is at least as low as predicted by generation-recombination theory; the shape is complex. Usually, two relaxation times and sometimes three are discernible. The spectrum often has a local maximum, even in thermal equilibrium. Several detailed three-and four-level models are described; their behavior is calculated and compared with experiment. The gross features of the spectra, viz., the temperature and light-intensity dependence of the relaxation times, the occurrence of negative plateau coefficients, and the interrelation between optical and thermal results can be explained if, besides the known gold levels, another level is postulated, situated slightly below the gold-acceptor level. Several features suggest that this level may stem from paired ionized gold-acceptor and shallow-donor impurities.