Appearance of a band of delocalized D− states in uncompensated silicon in an electric field

The impurity photoconductivity spectra of uncompensated silicon at liquid-helium temperatures under conditions of strongly suppressed background radiation (background) are studied in different electric fields E. It is established that the delocalization arising in the D− band as E increases is not associated with any changes of the fluctuation potential and is due to the direct action of the field E. A delocalization band of finite width appears abruptly at a critical value E c (∼100 V/cm) of E. The critical field E c increases with the density of charged centers in the sample.