COMPARISON OF PHOTOLUMINESCENCE LIFETIMES BETWEEN AS-PREPARED AND DRY-OXIDIZED POROUS SI

The photoluminescence decay of both as-prepared and dry-oxidized porous Si excited by a nitrogen laser pulse is not exponential, but is fitted well by two exponential decays with lifetimes ranging from a few nanoseconds to over 100 nanoseconds. Further, those lifetimes do not change with changing excitation power by more than three orders of magnitude. The lifetime of dry-oxidized porous Si is longer than that of as-prepared porous Si. These studies would suggest that the photoluminescence mechanism is basically the same for both as-prepared and dry-oxidized porous Si, and the radiative recombination path is through some luminescence centers lying in the widened band gap owing to quantum size effects.