Properties of deep Cu levels in GaP

Optical properties of two Cu-induced deep acceptorlike levels in GaP with binding energies E_A = 0.50 ± 0.01 eV and E_B 0.7 eV have been investigated. Data are reported here from purely optical techniques, based on detection of photoluminescence. A detailed spectral analysis of the broad Cu-related 1.65 eV-emission reveals a moderate Frank-Condon shift Δ_FC 105 ± 15 meV for the A-center. Accurate spectral data for optical cross section σ_pA⁰(hν) and σ_nA⁰(hν) were measured for the 0.50 eV A-center. Optical cross sections σ_pB⁰(hν) and σ_nB⁰(hν) could also be measured via luminescence, in spite of the fact that the B-center appears to have a completely nonradiative recombination.