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Hydrogenated nanocrystalline silicon was characterized using the transient photocapacitance (TPC) method. The TPC spectra show these materials to have a mixed-phase nature. At low temperatures, the spectra appeared very microcrystalline, whereas at moderate temperatures they appeared very similar to those for hydrogenated amorphous silicon. These differences are shown to result from the temperature dependence of the minority carrier collection from the nanocrystalline component. The effects of light-induced degradation were also studied. This caused a substantial decrease in minority carrier collection, similar to lowering the temperature of the undegraded sample. However, no concomitant increase in dangling bond defect density was observed.

The electronic properties of hydrogenated nanocrystalline silicon (nc-Si:H) were studied using junction capacitance methods. Drive-level capacitance profiling (DLCP) measurements revealed significant differences for nc-Si:H layers deposited under constant hydrogen dilution compared to those deposited using hydrogen profiling, with lower DLCP densities in the latter case. Transient photocapacitance (TPC) measurements revealed the mixed-phase nature of these materials. It disclosed spectra that appeared quite microcrystalline-like at lower temperatures, but more similar to a-Si:H at higher temperatures where the minority carrier collection is higher in the nanocrystalline component of these samples. This then suppresses the TPC signal from this component compared to the a-Si:H component. In contrast, because transient photocurrent signals are enhanced by the additional minority carrier collection, those spectra appear microcrystalline like at all temperatures. We also investigated the effects of light-induced degradation in these devices. This caused a dramatic decrease in hole collection, similar to that caused by reducing the measurement temperature of the samples. However, the light exposure did not appear to increase the deep defect density (dangling bonds).

In this paper, we present a comprehensive study of microcrystalline silicon thin film samples deposited by a novel growth process intended to maximize their grain size and crystal volume fraction. Using Atomic Force Microscopy, Raman spectroscopy, and x ray diffraction the structural properties of these samples were characterized qualitatively and quantitatively. Samples were grown using a Hot-Wire Chemical Vapor Deposition process with or without a post-growth hot-wire annealing treatment. During Hot-Wire Chemical Vapor Deposition, SiF 4 is used along with SiH 4 and H 2 to grow the thin films. After growth, some samples received an annealing treatment with only SiF 4 and H 2 present. These samples were compared to each other in order to determine the deposition conditions that maximize grain size. Large microcrystalline grains were found to be aggregates of much smaller crystallites whose size is nearly independent of deposition type and post-annealing treatment. Thin films deposited using the deposition process with SiF 4 partial flow rate of 2 sccm and post-growth annealing treatment had the largest aggregate grains ~ .5 µm and relatively high crystal volume fraction.

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