Photocapacitance investigation of stoichiometry-dependent deep levels in InP

The photocapacitance measurements under constant capacitance condition is applied to n- and p-type InP crystals prepared by 4h-annealing at 700°C under controlled phosphorus vapor pressure. Samples used are InP bulk crystals grown by the conventional LEC method. Vapour pressure controlled-zone melting grown InP and LPE-grown InP are also investigated. The phosphorus vapor pressure dependence of the deep level density is shown. And the excitation photocapacitance method is also applied to show the precise optical transition mechanism of these deep levels. From these results the defect formation mechanism is discussed in view of the deviation from the stoichiometric composition of InP