A possible model for changes in photoluminescence wavelength of porous Si due to photochemical etching

The changes in wavelength of photoluminescence (PL) along the depth directi on of porous silicon (PS) have been investigated using the well known photo chemical etching (PE) treatment technique. It was found that in both thicke r and thinner PS samples, there existed a range where the: PL output wavele ngth changed significantly from longer to shorter and irregular changes in the PL wavelength were observed. These results are in contrast with the res ult reported previously. On the basis of the band gap widening and the enha nced radiative recombination efficiency due to quantum confinement, i.e., q uantum size effect, a qualitative model to explain these behaviors was prop osed.