We report broad-spectrum electroluminescence (EL) in metal-insulator-silicon (MIS) tunnel diodes. In addition to Si-band-edge EL near 1.1 eV, hot-electron EL in Si can span a detector-limited range from 0.7 eV to 2.6 eV (1780 nm to 480 nm). The maximum EL photon energy increases with forward-bias voltage. In one implementation, sub-micron-size sites for light emission appear during forward-bias stress. The number of sites is linear in the applied current, consistent with formation of an anti-fuse at each site following breakdown of the insulator. We compare the post-stress current-voltage data to the quantum-point-contact model. Results are presented for various p-type Si(100) MIS devices having thin (8 nm or less) insulating layers of SiO2, Al2O3, and HfOxNy. We also describe novel MIS devices in which electron-beam lithography of an 18-nm-thick SiO2 insulator is used to define the EL sites.
We report general hot-carrier mechanisms for electroluminescence (EL) in metal-insulator-silicon tunnel diodes. We demonstrate these effects using various combinations of Si-oxide and Al-oxide tunnel-barrier insulators. In addition to an EL peak near the 1.1-eV Si band gap, we observe broad-spectrum EL that can span the detector-limited range from 0.7 eV to 2.6 eV (1780 nm to 480 nm). The maximum above-band-gap photon energy increases with the forward bias, consistent with hot-carrier recombination in Si. Below-band-gap EL is likely due to (i) hot-electron inter-conduction-band radiative transitions in Si and/or (ii) radiative recombination via localized interface states. Light emanates from specific sites with apparent size < 1 μm that appear during high-forward-current electrical stress. The number of sites can be in the hundreds, and is in direct proportion to the stress current, as anticipated for tunnel barrier dielectric breakdown. Current-voltage characteristics can be fit using a model appropriate to localized breakdown sites. Virtually all current is thought to cross the barrier at such sites, with local current densities as high as 108 A/cm2. We also describe novel devices where tunnelling occurs at predetermined sub-micron sites formed in 18-nm-thick SiO2 using electron-beam lithography and wet-chemical etching.
A fiberless 1-TW all-Nd:glass chirped-pulse amplification laser system is described in this paper. Starting from high-contrast 1-ps pulses produced directly from a Nd:glass feedback- controlled oscillator, this system employs a fiberless, gratings-only expansion/compression scheme, and produces clean (5 X 107 prepulse contrast) 1-J, 1.2-ps recompressed pulses without added pulse-cleaning. The same system can also be configured to produce up to 5-J uncompressed 410-ps pulses. A novel subpicosecond cross-correlation technique is also described.
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