Chemical design of direct-gap light-emitting silicon

Quantum confinement effect has been the dominant approach guiding the search for light-emitting silicon. By first-principles total energy calculations of Si delta-doped with oxygen layers, however, we show that this generally accepted mechanism is ineffective. Instead, a different mechanism is proposed based on defect engineering where the oxygen atoms chemically shift the valence band edge of Si away from the zone center, resulting in the desired optical functionality. Our calculation suggests new design principles for light-emitting silicon as well as providing the microscopic origin for the observed strong luminescence and band gap increase in the SiO(001) multi-delta-layers.