Dense electron-hole plasma in silicon light emitting diodes

Efficient electroluminescence of silicon light emitting p-n diodes with different sizes and shapes is investigated at room temperature. High quantum efficiency of the diodes, a long linear dependence of the electroluminescence intensity on the diode current and a low energy shift of the emission line in electroluminescence spectra with increasing diode current are explained by the self-compression of injected electron-hole plasma into dense electron-hole plasma drops. Experiments on space scanning of the electroluminescence intensity of the diodes support this conclusion. The plasma self-compression is explained by existence of an attraction in electron-hole plasma, compensating the plasma pressure. A decrease of the semiconductor energy gap due to a local lattice overheating, produced by the plasma, and the exchange-correlation interaction could contribute to this attraction. The self-focusing of the injection current can accompany the plasma self-compression.