Properties of theEL2 level inGaAs1−xPx

In this paper the properties of the EL2 level are studied as a function of the composition x in the alloy system ${\mathrm{GaAs}}_{1\mathrm{-}\mathrm{x}}$ ${\mathrm{P}}_{\mathrm{x}}$. From photoionization cross sections and thermal emission data the ground state of the EL2 level can be followed through the alloy system with respect to energy position, spectral details in optical cross sections, and thermal emission rates giving information on how the ground and excited states vary relative to the band structure in the alloy. Comparing our data extended to GaP with published properties of GaP defects we strongly reduce the number of candidates for an EL2-related defect in GaP, and tentatively suggest a candidate for a defect in GaP corresponding to EL2. The limited composition range in which the metastable state of EL2 has been observed is found to coincide with compositions for which the excited EL2 state is degenerate in energy with the conduction band.