Optical spectroscopy of the trivalent silicon defect at the Si-SiO2interface

Optical absorption by the trivalent silicon defect at the Si-${\mathrm{SiO}}_2$ interface has been measured by electroabsorption spectroscopy. On metal-oxide–silicon (MOS) capacitors, electric field modulation of the occupancy of the silicon dangling orbitals is directly detected as a synchronous modulation of the absorption of subband gap light; in passivated capacitors, a residual absorption is detectable because of free carriers in the accumulation layer of the MOS structure. Both photon energy and surface-potential controlled trap occupancy provide probes of the interface-state distribution. In addition, the results provide an estimate of ${10}^{\mathrm{-}17}$ ${\mathrm{cm}}^2$ (at 1 eV) for the effective optical cross section of the 0→1 electron transition of the interfacial defect.