Ballistic transport and photoluminescence in silicon nanocrystallites

One of the most interesting problems of modern solid-state physics is the emission mechanism of bright photoluminescence in the red spectral range discovered in silicon nanocrystallite structures, particularly in wires and dots. This article presents an interpretation of strong "red" photoluminescence in silicon wires and dots based on hot carrier ballistic transport in the process of photoluminescence excitation. Photoluminescence (PL), its excitation, electron paramagnetic resonance, infrared absorption and Raman scattering spectra of as-prepared Si wires have been examined. Silicon wire layers (porous silicon) were obtained by electrochemical etching of p-type Si wafers in a HF-ethanol solution. An atomic force microscope is used for porous silicon morphology analysis. It is shown that the very low PL intensity could be attributed to carrier radiative recombination between localized states quantum confined inside Si nanocrystallites. It is revealed that the ballistic effect can enhance the effective hot carrier excitation of interface defect-related photoluminescence in Si nanocrystallite structures. PL excitation spectrum modification depending on the Si crystallite size confirms the role of the ballistic effect in PL excitation of Si low-dimensional structures.