Energy bands in quantum confined silicon light-emitting diodes

Measurements of the temperature dependence of the current-voltage characteristics of heterojunction light-emitting diodes fabricated by depositing indium tin oxide onto the surface of electrochemically etched p-type silicon (porous silicon) are presented, and the results are compared with those for adjacent devices formed on nonprocessed bulk silicon. The barrier height for the diodes which exhibit quantum confinement effects was determined to be 0.42 eV. Unlike the bulk silicon devices, the diodes prepared on porous silicon did not manifest a photovoltaic effect. These observations allow us to present a potential energy diagram for porous silicon heterojunction diodes which indicates barriers in both the conduction band and the valence band.