Diffusion, Solubility, and Electrical Properties of 64Cu in GaSb Single Crystals

The behavior of 64Cu in as-grown and bent crystals of GaSb has been investigated in order to obtain information on the nature of the native defects supposedly present in this crystal. 64Cu concentrations were determined radiochemically and Hall measurements were made before and after the introduction of the 64Cu. Although interstitial Cu diffuses very rapidly into as-grown GaSb, the rate of substitution of Cu is found to be extremely slow, even at temperatures 30°C from the mp. The rate of substitution is greatly accelerated in bent GaSb specimens. Measurements on these show that ∼1019 cm−3 Cu dissolves at the maximum (650°). Curves for the interstitial and substitutional solubilities are given. Hole concentrations (25°C) in bent specimens saturated with Cu are only ∼⅓ of the 64Cu concentrations over a large Cu concentration range. This suggests that a considerable fraction of the Cu precipitates from solution during quench to room temperature. Hall curves on such specimens show four distinguishable acceptor levels. Hall measurements on as-grown GaSb indicate that the native defect is a double acceptor as previously suggested by others. The low interstitial Cu solubility observed at 250–350°C indicates that the native acceptors are not Ga vacancies. GaSb does not exhibit the ``doubling'' phenomenon toward 64Cu such as found in GaAs.