QUANTUM CONFINEMENT IN THE SI-III (BC-8) PHASE OF POROUS SILICON

Porous silicon was recently shown to give rise to the same semimetalli c Si-m (BC-8) phase as silicon upon application and release of high pr essure. This phase is known to have a direct gap and we examine the ef fect of quantum confinement on its electronic structure. This is perfo rmed by combining empirical tight binding and ab initio local density calculations. The blue shift is found to be similar to what is obtaine d for nanocrystallites with the diamond structure and the radiative re combination rate is much larger. Comparison with experiment shows that the observed luminescence is not consistent with the quantum confinem ent hypothesis. (C) 1997 American Institute of Physics.