Deep levels related to Co in InP

Electrical and optical junction space-charge spectroscopies, photoluminescence, and electron paramagnetic resonance are used to investigate the charge states of Co present in n-type InP and to characterize the deep levels occuring in such Co doped materials. Electron paramagnetic resonance and photoluminescence results indicate unambiguously that the Co2+ charge state is present in n-type material substitutional to indium. Only one deep level at EV +0.24 eV is detected with a concentration similar to Co doping. The (EV +0.24 eV) level is identified with the (Co2+→Co3++eCB) charge state change mainly on the analysis of its optical cross sections σ0n (hν) and σ0p (hν). Optical transitions are well interpreted as transitions from the Co2+ ground state (4A2) to the Γ point minimum of the conduction band for σ0n (hν) and from the valence band to the Co2+ ground (4A2) and excited state (4T2) for σ0p (hν). The value of the ionization energy for Co2+ in InP (1.16 eV) is shown to agree quite well the value predicted by the trends of the ionization energies of 2+ charge states of transition metals in III-V semiconductors.