Method for Direct Determination of the Effective Correlation Energy of Defects in Semiconductors: Optical Modulation Spectroscopy of Dangling Bonds

The optical modulation technique is used for direct determination of energy levels and the effective correlation energy $U_{\mathrm{eff}}$ of dangling-bond defects. With an accuracy of 0.1 eV we found for the dangling-bond defect in $a$-Si: H, $U_{\mathrm{eff}}=0.5\mathrm{}$ eV; in $a$-${\mathrm{As}}_2$${\mathrm{S}}_3$, $U_{\mathrm{eff}}=-1.0\mathrm{}$ eV; in ${\mathrm{As}}_2$${\mathrm{Se}}_3$, $U_{\mathrm{eff}}=-0.7\mathrm{}$ eV; and in trans-${\left(\mathrm{CH}\right)}_x$, $U_{\mathrm{eff}}=0.95\mathrm{}$ eV.