Influence of native defects on formation absorption spectra of InP crystals

摘要

Optical absorption measurements have been carried out on semi-insulating and n - type InP:Fe , InP:Sn.. The optical absorption spectra of InP:Fe contain several broad structure-free bands due to charge conduction between Fe ions and band states. However, in the case of InP high doped with Sn, the same absorption band with threshold at 0.64 eV was detected. It is usually attributed to the excitation of electrons from the ground state of one electron trap Fe~(2+) to the Γ -point conduction band minimum. The spectral photo-ionization cross-section approximation is made on the basis of a phenomenological model for an admixture center with an attracting δ - potential in the vicinity of the admixture and Coulomb potential at large distances. A weak electron- phonon interaction is taken into account. High quality of approximation was found. The analysis of the absorption spectra and ionization energies allows to expect that absorption zone with the threshold 0.64 eV occurs due to deep ionized acceptors that are charged indium vacancies.