Time-resolved photoluminescence spectra of strong visible light-emitting SiC nanocrystalline films on Si deposited by electron-cyclotron-resonance chemical-vapor deposition

SiC nanocrystalline films on Si substrates deposited using advanced electro n-cyclotron-resonance chemical-vapor deposition exhibit intense visible lig ht emission at room temperature under laser excitation. Continuous-wave and time-resolved photoluminescence measurements for these SiC films were carr ied out at room temperature. The photon energy of the dominant emission pea ks is higher than the band gap of cubic SiC. Room-temperature optical absor ption measurements show a clear blueshift of the band gap of the samples wi th a decrease of the average size of the nanoclusters, indicating an expect ed quantum-confinement effect. However, the emission spectra are basically independent of the size. Temporal evolution of the dominant emissions exhib its double-exponential decay processes. Two distinct decay times of similar to 200 ps and similar to 1 ns were identified, which are at least two orde rs of magnitude faster than that of the bound-exciton transitions in bulk 3 C-SiC at low temperature. Strong light emissions and short decay times stro ngly suggest that the radiative recombinations may be from some direct tran sitions such as self-trapped excitons on the surface of the nanoclusters. ( C) 2000 American Institute of Physics. [S0003-6951(00)04618-0].