COMPARISON OF ROOM-TEMPERATURE PHOTOLUMINESCENCE DECAYS IN ANODICALLYOXIDIZED CRYSTALLINE AND X-RAY-AMORPHOUS POROUS SILICON

The photoluminescence (PL) decay after pulsed YAG:Nd excitation at 353 nm of anodized p-type porous silicon layers (either PECVD-deposited X -ray-amorphous or bulk crystalline) has been studied as a function of PL wavelength in the ns to ms time range. The decays are similar for b oth materials, being strongly non-exponential with a slow (typically 1 0-100 mu s) and a fast (<50 ns) component, the latter being stronger i n X-ray-amorphous films. The only major difference occurs at large wav elengths (above 750 nm), where the slow component of the decay in the amorphous layer becomes quite different from the ''universal'' [1] lin e shape observed in its crystalline counterpart, which is shown here t o be that of a stretched exponential. These observations are borne out by delayed PL spectra obtained with a boxcar integrator in the same t ime range. We discuss various decay analysis procedures leading to an effective recombination rate distribution and compare the results deri ved for both types of material.