MORPHOLOGY OF POROUS SILICON STRUCTURES FORMED BY ANODIZATION OF HEAVILY AND LIGHTLY DOPED SILICON

By computer simulation the growing process of porous silicon under p(- )-Si and p(+)-Si anodization in HF solution is studied. The model of e lectrochemical etching of p(+)-Si includes the relief selective mechan ism, which allows one to establish the relationship between anodizatio n conditions (current density, HF concentration, temperature and dopin g level) and the topological characteristics of porous silicon (PS). T he simulation of p(-)-Si dissolution is based on the model of diffusio n limited aggregation (DLA), taking into account the thermal generatio n of holes and the quantum confinement effect. The various morphology of simulated PS structures exhibits a close resemblance to that of exp erimental ones formed in p(+)-Si and p(-)-Si wafers. For simulated p(- )-Si-based PS layers the porosity profiles and fractal dimension are c alculated. It is shown that PS in p(-)-Si is multifractal with fractal dimension varying monotonously from 0.1 to 3 with size increase. (C) 1998 Elsevier Science S.A. All rights reserved.