Plasma Immersion Ion Implantation (PIII) excels in several areas over conventional ion implantation, for example, higher dose, shorter implantation time, and lower overall cost. The technique can be used to fabricate buried porous silicon. In our experiment, hydrogen is implanted into Si by PIII at 5–30kV to form underlying porous silicon (PS) which emits light at an energy higher than the Si bandgap. The optical properties of the PS samples as measured by photoluminescence are quite good. The PHI technique therefore offers an alternative means to fabricate buried porous silicon structures which can potentially be used to fabricate optoelectronic devices in silicon.