Gamma Irradiation of Silicon. I. Levels in n-Type Material Containing Oxygen

The resistivity and Hall coefficient of n-type silicon containing oxygen have been measured as a function of temperature before and after a number of successive irradiations in a Co60 gamma-ray source. A net acceptor level 0.17 ev below the conduction band was observed to result from the irradiation. Its rate of introduction was 7×10−4 traps/cm3 per photon/cm2 in 50- ohm-cm material and was about twice that in more heavily doped material (∼2 ohm-cm). Acceptor levels, lying deep within the forbidden gap, were also observed. Their total introduction rate was smaller than that of the 0.17-ev level by a factor of 50. A lowering of the mobility below ∼100°K was also a result of the irradiations. In heavily irradiated samples this lowering of the mobility was much greater than could be explained on the basis of point-charge scattering.