Narrow Results

We present the modification of optical transition probability in the superlattices (SLs) due to the presence of structural defect and the variation of layer thickness. The results show that optical transition probability between two bound states is mainly determined by the thicknesses of layer in defect region and its nearest constituent layers for a symmetric structure. When the well layer thickness varies, the variation of transition probabilities between two bound states depend on the parity of the index of minigap n, while those from the bound states to the delocalized scattering is irrelevant to n. It is believed that applying appropriate structure and layer thickness may enhance the optical transition probability in designing optical device.

Photoluminescence, photoabsorption, and X-ray photoelectron spectroscopic study revealed that an optical transition of porous silicon from red-shift to blue-shift, and Si-2p binding energy transition from low to high at a critical anodization temperature, 343 K. Possible origin for the reverse variations happening at temperature below and above the critical temperature is discussed.