Variation of the midgap electron traps (EL2) in liquid encapsulated Czochralski GaAs

Abstract

We have characterized the midgap electron trap (so far believed to be EL2) in liquid encapsulated Czochralski GaAs by measuring deep level transient spectroscopy spectra, and found more than two midgap electron traps which can be classified into two groups. A trap belonging to the first group is rather stable in its properties and the other is unstable. The capture cross section of the levels in the latter group varies continuously in depth from the surface and also is changed by thermal annealing. We discuss these characteristics in connection with growth conditions.