Modeling of light-emission spectra measured on silicon nanometer-scale diode antifuses

Electroluminescence (EL) spectra of nanoscale diodes formed after gate-oxide breakdown of n⁺ -polysilicon/oxide/p⁺-substrate metal-oxide-semiconductor capacitors were measured in reverse and forward bias. The nanoscale diodes, called diode antifuses, are created by the formation of a small link between the n⁺ -poly and the p⁺ -substrate with the properties of a diode. A previously published multimechanism model for avalanche emission from conventional silicon p-n junctions is applied to fit the EL spectra in reverse-biased silicon-diode antifuses. The results show that the light from reverse-biased diode antifuses is caused by the same phenomena as in conventional p-n junctions. Forward-bias spectra of the diode antifuses show different shapes when lightly or highly doped p substrates are used. In the case of a lightly doped p substrate, the EL intensity in the forward mode is increased by about two orders of magnitude in the visible-wavelength range with a maximum intensity in the infrared region. A phonon-assisted electron-hole recombination model is applied to fit the low-energy part of emitted spectra. The visible emission is attributed to the Fowler-Nordheim tunneling current through the SiO₂, enabled presumably by electron capture into SiO₂ trap levels and intraband transition of hot electrons injected into the Si bulk.