Transient capacitance spectroscopy in polycrystalline silicon

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Abstract
We have performed deep level transient spectroscopy (DLTS) on 5 Ω cm p-type polycrystalline silicon. Typical DLTS spectra exhibit three peaks centered at 250, 300, and 340 K. The density of states which is estimated from these spectra is found to extend from 0.18 eV of the valence band with a density ∼ 2×1015 eV−1 cm−2. Measurements of capture rates have shown a characteristic trap filling time of ∼10−3 s corresponding to an apparent capture cross section of the order of 10−21 cm2. Studies of the passivation (in a deuterium plasma) of these boundary states have also been made. In that case, the DLTS spectra present only one significant peak at 245 K; the density of states of the unpassivated material is reduced to localized states centered at 0.32 eV from the valence band with a concentration of 5.6×1014 cm−2. The capture cross section of these states is 3.7×10−20 cm2.