Interpretation of deep-level optical spectroscopy and deep-level transient spectroscopy data: Application to irradiation defects in GaAs

A detailed theoretical analysis of deep-level transient spectroscopy and deep-level optical spectroscopy data is worked out with application to some irradiation centers in GaAs. A simple model including the local point-defect symmetry is proposed to deduce from experiment the physical parameters characterizing the defects. The originality of the proposed method is to extract from the experimental results quantities corresponding to "ionization energies at zero distortion," which are directly comparable to the predictions of available theoretical calculations. For this the optical line-shape function is represented by a Gaussian curve adjusted to reproduce the exact first two moments, in the case of degenerate electronic states. An application is made to the case of $E_1$ and $E_2$ in GaAs where the hypothesis that these centers correspond to two consecutive charge states of the arsenic vacancy $V_{\mathrm{As}}$ is explored. Comparison between theory and experiment strongly supports the identification of $E_1$ and $E_2$ with $V_{\mathrm{As}}^{2-}$ and $V_{\mathrm{As}}^{-}$, respectively.