Bandgap widening in quantum sieves

Dense distributions of separate insulating regions in silicon may produce Anderson localization and hence a kind of confinement. This weak confinement is expected to be responsible for visible photoluminescence with different features from that observed in porous or nanocrystalline silicon. Dense distributions of separate insulating regions may be produced by ion implantation of a suitable species followed by an appropriate heat treatment. The visible photoluminescence observed in ion-implanted Si:H, Si:O and Si:He is explained in terms of exciton weak confinement.