Raman scattering study of photoluminescent spark-processed porous InP

Raman scattering has been used to study porous InP (001) samples prepared b y the application of high voltage spark discharges in air and argon atmosph eres. For photoluminescent material, Raman scattering as well as Normaski m icroscopy of a transversally cut sample, (011) face, show the existence of two very distinct zones, that lie at different depths: a superficial lumine scent region constituted mostly by In2O3 and InPO4 oxides, and a second adj acent deeper zone formed by damaged InP. These results highlight the role t hat the oxidation plays in this material as source of the visible luminesce nce that the material emits when excited with UV radiation. The deepest reg ion shows InP-like vibrational behavior with broad longitudinal optical (LO ) and transversal optical (TO) phonon bands. A fit of the observed lineshap es of the TO and LO modes using the spatial correlation model provides an e stimate of the size of the crystalline regions (L similar to 30 Angstrom). (C) 2000 Elsevier Science B.V. All rights reserved.