Formation of < 001 >-aligned nano-scale pores on (001) n-InP surfaces by photoelectrochemical anodization in HCl

[001]-oriented nanometer sized straight pores without branches were formed for the first time on (001) n-type InP surfaces by photoelectrochemical ano dic reaction in HCl. The pore diameter, wall thickness and pore length coul d be changed in the ranges of 110-250 nm, 16-50 nm and 17-80 mm, respective ly, by changing the anodizing overpotential and time. Based on the diffusio n limited model for porous Si formation, the formation of [001]-aligned str aight pores without branches on n-type InP was explained in terms of the sh ort lifetime of holes combined with the presence of a strong electric held at the pore tip. Contrary to the expectation of blue-shifted photoluminesce nce (PL) emission due to quantum confinement at pore walls, porous (001) In P samples exhibited intense red-shifted PL peaks. This was explained by for mation of a set of well defined new surface state levels on the anodized wa ll surfaces of pores. (C) 1999 Elsevier Science S.A. All rights reserved.