Possible Mechanism of the 30–100 Picoseconds Fast and Efficient Photoluminescence From nc-Si/a-SiO2Doped with Transition Metals

The nc-Si/a-SiO2composite thin films doped with tungsten show very fast and efficient photoluminescence (PL). In order to obtain insight into the PL mechanism we have performed a comparative study with other metals. The results lend support to the suggested mechanism which includes the photogeneration of charge carriers due to efficient absorption of the excitation UV light in the silicon nanocrystals followed by energy transfer to the Wn+radiative center from which the light emission occurs.

Defect-Related Photoluminescence of a-Si:H

ABSTRACTThe defect-related photoluminescence (0.8–0.9eV) of a-Si:H is studied as a function of the defect density ND and the temperature using subgap excitation of Ex= 1.16eV. Electron bombardment, light exposure and phosphorus doping were employed to create defects. The defect density ND was infered from CPM- and PDS-spectroscopy. We conclude from the measured density-of-states distributions of doped films that the radiative process is tunneling of bandtail carriers (Majority carriers) into the defect states. The dependence of the emission intensity on ND suggests that only a subgroup of the defects acts as radiative center. We propose that the local structure of the defect determines whether it acts as radiative or nonradiative center.