Enhancement in the efficiency of light emission from silicon by a thin Al_2O_3 surface-passivating layer grown by atomic layer deposition at low temperature

摘要

Thin Al_2O_3 surface-passivating layers grown by atomic layer deposition at 100 ℃ were demonstrated to be instrumental in producing efficient light emission from silicon. External quantum efficiency up to 1.3 x 10~(-4) was observed from silicon metal-insulator-semiconductor light-emitting diodes with a 5 nm Al_2O_3 surface-passivating layer as the insulator, which is more than tenfold that from similar devices with a 5 nm SiO_2 insulator layer thermally oxidized at 1000 ℃. Anomalous temperature dependences of the photoluminescence intensities and spectra at low temperatures indicate the presence of bound excitonic traps at the Al_2O_3/Si interface. The enhanced light emission may be attributed to the temporary capture of excitons by the interfacial bound excitonic traps, which effectively reduces nonradiative recombination.