Electroluminescence at Si bandgap energy from metal-oxide-semiconductor tunneling diodes

We report room-temperature electroluminescence at Si bandgap energy from Metal-Oxide-Semiconductor (MOS) tunneling diodes. The ultrathin gate oxide with thickness 1 to approximately 3 nm was grown by rapid thermal oxidation (RTO) to allow significant current to tunnel through. The measured EL efficiency of the MOS tunneling diodes increases with the injection current and could be in the order of 10-5, which exceeds the limitation imposed by indirect bandgap nature of Si. We also study the temperature dependence of the electroluminescence and photoluminescence. The electroluminescence is much less dependent on temperature than photoluminescence from Si. The applied external field that results in the accumulation of majority carriers at Si/SiO2 interface in the case of electroluminescence could be the reason for such difference. The involved physics such as optical phonon, interface roughness, localized carriers, and exciton radiative recombination are used to explain the electroluminescence from silicon MOS tunneling diodes.