Impurity pairs and relaxation of excitation in silicon doped with group III and V impurities

In Si doped with group III and V impurities at concentrations of 10¹⁶–10¹⁸ cm^–3 infrared absorption bands of impurity pairs (IPs) appear and there is a slow relaxation of polarization hopping photoconductivity (PC) in a microwave (MCW) electric field. IPs create a broad spectrum of local states with ionization and excitation energies both lower and higher than those of single-impurity atoms. It is shown that ionization of IPs in compensated Si and a slow relaxation of re-charge after extrinsic excitation give a principal contribution to PC, due to hopping transitions of carriers between ionized and neutral impurity atoms in IPs induced by a MCW electric field.