Control of the crystallite size and passivation of defects in porous silicon by a novel method

Porous silicon films were prepared by lateral anodization of crystalline silicon in HF based solutions at different current densities. At an optimum current density, passivation of the defects by an appropriate post-anodization treatment results in the significant enhancement in the photoluminescence (PL) efficiency. However, above the optimum current level, a phase is obtained which shows significant broadening of the PL spectrum indicating the quantum wire size distribution. The degraded PL intensity in the treated samples is higher as compared to that for the as-anodized samples. Infrared vibrational studies indicate that this enhancement is due to the H-passivation of defects in the Si-pore interface, though the presence of hydrogen-terminated silicon clusters cannot be ignored. Capacitance-voltage studies concur well with the photoluminescence and infrared results.