Optical properties of the main electron-irradiation-induced defects inp-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 σₚ⁰ 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.