Far-infrared absorption was investigated in n-type Czochralski-grown material which was saturated with H and irradiated with fast electrons. Two series of absorption bands (200 to 330/cm) were observed after post-irradiation annealing of the crystals at 300 to 550C. These bands were associated with ground to excited-state electronic transitions in 2 types of shallow donor (with ionization energies of 0.037 and 0.0426eV), which could be described by the effective-mass approximation. These donors were related to defects which had previously been detected by means of electrical measurements. The development of one type of center seemed to be associated with transformation of the other center. The preliminary results indicated that H and O atoms, together with some radiation-induced defects, were included in these centers. One center was associated with a configuration of the negative-U defect which had previously been detected by means of electrical measurements. This defect had an occupancy level at Ec-0.075eV.

V.P.Markevich, M.Suezawa, K.Sumino, L.I.Murin: Journal of Applied Physics, 1994, 76[11], 7347-50