The single crystal growth and electrical properties of cobalt-doped indium phosphide

Abstract

It is shown that semi-insulating properties can be induced in single crystals of indium phosphide grown by the liquid encapsulation Czochralski technique by using cobalt as a dopant. A mean value of segregation coefficient for cobalt in InP equal to 4 × 10−5 has been determined. Precipitation of a phosphide of cobalt is shown to limit the yield of useful semi-insulating material at high cobalt concentrations. The onset of semi-insulating behaviour occurs at a cobalt concentration in the crystal which equates approximately to the residual background concentration of n-type carriers. The close analogy of this behaviour with that observed in iron-doped crystals suggests that the semi-insulating properties are derived from Co2+ energy states which are shown to be present in these cobalt-doped crystals.