A transient capacitance-voltage method was proposed for the measurement of the net donor concentrations, free electron concentrations and space-charge distributions of Schottky diodes on Si-doped AlGaAs. This method was used to deduce the binding energy of the DX center from the temperature-dependent free electron concentration. Comparisons of theory and experiment for the space-charge distribution were made for the positive-U and negative-U models of DX centers. It was noted that a single negative-U DX level could not alone explain the experimental results. In order to understand experimental data on DX centers within the framework of the negative-U model, large concentrations of ionized shallow donors had to be assumed. Previously observed multi-DX levels were suggested to be a possible explanation for the existence of such ionized shallow donors. Overall, the present data were in somewhat better agreement with the positive-U model than with the negative-U model. It was concluded that it was unclear whether the transient capacitance-voltage method could furnish unambiguous data on the energetic structure of deep centers.

Y.B.Jia, H.G.Grimmeiss, M.F.Li: Semiconductor Science and Technology, 1996, 11[12], 1787-90