Shallow donor associated with the main electron trap (EL2) in melt-grown GaAs

A systematic analysis of Hall effect measurements on a large number of melt-grown GaAs crystals with different concentrations of the major deep trap (EL2) revealed the presence of a new shallow donor level (20–30 meV below the conduction band) with concentrations similar to those of the EL2. This finding indicates that the EL2 center is a double donor consisting of the deep EL2 donor at Ec−0.76 eV and a shallow donor state. The presence of the shallow donor state should have important consequences in the formulation of a compensation mechanism in semi-insulating GaAs.