Radiative recombination and filling effect of surface states in porous InP

Porous InP samples prepared by wet electrochemical anodization techniques are studied by photoluminescence (PL) spectroscopy at 25 K. The PL of as-grown porous InP shows redshift with respect to that of bulk InP. The PL emission is very sensitive to chemical and heat treatment. For instance, the PL obtained from the AgNO3 treated sample shows a blueshift with respect to that of the bulk InP. Moreover the PL spectra from the as-grown porous sample and the AgNO3 treated sample exhibit opposite shift trend on excitation levels. The PL of the AgNO3 treated sample shifts slightly to lower energies with increasing excitation levels, which is similar to that of the bulk InP, while the PL of the as-grown porous InP shifts obviously to higher energies, which is explained by the filling effect of surface states.