TIME-RESOLVED PHOTOLUMINESCENCE OF POROUS SILICON - EVIDENCE FOR TUNNELING LIMITED RECOMBINATION IN A BAND OF LOCALIZED STATES

Time resolved photoluminescence of porous silicon at room temperature was measured for several emission energies under 2 ns nitrogen laser e xcitation. For each emission energy studied there is a broad distribut ion of lifetimes extending over a few decades. The mean value of the d istribution varies with the emission energy, from 3 (2.77 eV) to 50 mu s (1.96 eV). The results can be explained by assuming a tunneling limi ted recombination mechanism between bands of localized states. We asso ciate this behavior with a superficial disordered Si:O:H compound rath er than with quantum confinement effects.