STUDY OF THE DEEP ACCEPTOR LEVELS OF IRON IN INP

The measurement of photoconductivity in samples of semi-insulating n-type Fe-doped InP are reported. Optical transitions are interpreted as between Fe3+, Fe2+ and Fe+ ions and the conduction and valence bands, as well as an internal transition of the Fe2+ level. The relative strengths of the transitions observed are found to depend strongly upon the doping of the samples due to the change of the concentration of the different ion species present. A level scheme of the energy of the acceptors at 6K (300K) is deduced to consist of an Fe2+ ground state 0.64 eV (0.66 eV) below the Gamma -point conduction minimum with an excited state of Fe 2+ 0.351 eV (0.351 eV) above the ground state. A two-electron trap state Fe+ is believed to lie 0.34 eV (0.28 eV) below the conduction band. Transitions are also thought to occur to higher satellite valleys of the conduction band located at 0.62 eV (0.42 eV) above the Gamma -point minimum.