Effects of stoichiometry on deep levels in MOVPE GaP

Epitaxial layers of GaP have been grown using different phosphorus pressures. The materials have been investigated using space charge techniques and injection luminescence (IL). Six deep levels and six luminescence bands have been characterised. The concentrations of some deep levels and some of the IL bands were found to depend strongly on the stoichiometric conditions during growth. These deep levels are tentatively connected to two of the charge states of P_Ga(P_Ga⁴⁺ and P_Ga³⁺) and to Ni_Ga. Of the IL bands, two are suggested to be related to the same defect as the deep levels, i.e. to the two charge states of P_Ga, and one to pair spectra involving the deep oxygen donor.