Urc 97134 Surface States and Effective Surface Area on Photoluminescent P - Type Porous

The present study is motivated by the possibility of utilizing porous silicon for spectral sensors. Pulse measurements on the porous-Si/electrolyte system are employed to determine the sufiace effective area and the surface-state density at various stages of the anodization process used to produce the porous material. Such measurements were combined with studies of the photolurninescence spectra. These spectra were found to shift progressively to the blue as a iimction of anodization time. The luminescence intensi~ increases initially with anodization time, reaches a maximum and then decreases with fimther anodization. The surface state density, on the other hand, increases with anodization time from an initial value of -2x1 012 cm-z for the virgin surface to -1013 cm-2 for the anodized surface. This value is attained already after -2 rnin anodization and upon firther anodization remains fairly constant. In parallel, the effective surface area increases by a factor of 10-30. This behavior is markedly different from the one observed previously for n-type porous Si.