OPTICAL-PROPERTIES OF THE MAIN ELECTRON-IRRADIATION-INDUCED DEFECTS IN P-TYPE INP - COMPARISON WITH CALCULATIONS FOR THE ISOLATED AND ACCEPTOR-PAIRED PHOSPHORUS VACANCY

Optical capacitance spectroscopy and thermal annealing of defects have been used to study both the electron traps EP1,E11 and the dominant hole traps (H3-H4-H4) produced by low-energy electron irradiation in Zn-doped p-type InP. This shows that the 1.1-eV onset in the photoionization cross sections (PCS's) previously attributed to (H3-H4) is actually due to the unrelated electron trap EP1. The true PCS's p0 of (H3,H4) are compared with PCS tight-binding Green's function calculations to test the earlier proposal that the (H2-H3-H4-H4,E11) series might arise from different states of (VP-Zn) complexes. The model yields an effective agreement as concerns both the energy location of the hole-levels series in the forbidden gap and the vanishingly small contribution to the PCS's of the four equivalent L valence-band minima. The proposal that E11 might correspond to the ionization of an e state of the VP-Zn complex also agrees with the experimental observation of both optical transitions to the valence band and to the conduction band but cannot account for the midgap position of E11. © 1990 The American Physical Society.