The optical properties of porous silicon produced by metal-assisted anodic etching

Porous silicon (PS) was obtained from n-type (100) mono-crystalline silicon wafers with different metal using two different illumination conditions. The visible photoluminescence (PL) may come from defect-related radiative centers on PS surface and adsorbed hydrogen atoms may be associated to the elimination of irradiative centers on PS surface, which can be proved by the infrared absorption spectra. The metal can be used as catalytic role to increase the etching rate under back illumination, but under front illumination, the metal can cancel light-generated carrier leading to the decrease of etching rate during anodic etching. Furthermore, the change of minority carrier lifetime is opposite to the change of PL efficiency of PS, which can be Confirmed by the results of l-PCD measurements.