Infrared absorption of the 78-meV acceptor in GaAs

We observe the infrared absorption spectra associated with a residual 78-meV acceptor in undoped liquid encapsulated Czochralski GaAs. The acceptor appears to be associated with an intrinsic defect, most likely the antisite GaAs. This acceptor is the dominant level in material grown from heavily Ga-rich melts. The concentration of the level depends strongly on melt stoichiometry increasing from about 3×1015 cm−3 to 3×1016 cm−3 as the As atom fraction changes from 0.47 to 0.43.