Transient Capacitance Spectroscopy (DLTS) in Metal-Oxide-Semiconductor structures is usually analysed assuming that the only contribution to the variations in the semiconductor surface capacitance originates in detrapping of carriers from defects at the Si/SiO2 interface or in the Si or SiO2 bulks. Using original pulse configurations, we have detected, in all samples investigated, capacitance transients which cannot be accounted for by such classical emission mechanisms but are in accordance with a dipolar relaxation mechanism. After each pulse, the relaxation follows the electric field direction with a distributed time constant, almost independently of temperature and applied electric field (from 35 K up to 200 K). We further explain why these dipolar relaxation effects could not be observed easily via the usual capacitance or conductance measurements. The physical origin of these dipolar relaxations is briefly discussed.
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Rosencher et al. (1984) studied this question.