Electroluminescence studies in silicon dioxide films containing tiny silicon islands

Electroluminescence from metal-insulator-semiconductor structures with silicon dioxide (SiO2) layers containing varying amounts of excess silicon (Si) in the form of tiny Si precipitates have been studied in detail. Bulk insulator emission from the Si islands is shown to dominate over emission from either the SiO2 matrix material or the metallic gate material by studies of oxide or metal gate material, voltage polarity, and insulator thickness dependencies. Several distinct spectral peaks are observed in the energy range from 1.5 to 5 eV which cannot be attributed to optical interference effects. The higher-energy peaks show a strong dependence on electric field relative to that at the lowest energy (1.7–2 eV). The entire spectral amplitude shows a strong dependence on high-temperature annealing and excess Si content, decreasing drastically with increasing Si or decreasing annealing temperature. These results are shown to be consistent with light emission during electronic transitions between discrete energy levels associated with Si islands and/or their interface with the SiO2 host matrix material. Quantum size effects, similar to those observed in semiconductor superlattices, are proposed as one possible explanation.