Snapback-Free Reverse-Conducting SOI LIGBT with an Integrated Self-Biased MOSFET

A novel snapback-free RC-LIGBT with integrated self-biased N-MOSFET is proposed and investigated by simulation. The device features an integrated self-biased N-MOSFET(ISM) on the anode active region. One side of the ISM is shorted to the P+ anode electrode of RC-LIGBT and the other side is connected to the N+ anode via a floating ohmic contact. The adaptively turn-on/off of the ISM contributes to improve the static and dynamic performance of the ISM RC-LIGBT. In the forward-state, due to the off-state of the ISM, the snapback could be effectively suppressed without requiring extra device area compared with the SSA (separated shorted anode) and STA (segmented trenches in the anode) LIGBTs. In the reverse conduction, the ISM is turned on and the parasitic NPN in the ISM is punched through, which provides a current path for the reverse current. Meanwhile, during the turn-off and reverse recovery states, the ISM turns on, providing a rapid electron extraction path. Thus, a superior tradeoff between the on-state voltage drop (Von) and turnoff loss (Eoff) as well as an improved reverse recovery characteristic can be obtained. Compared with the STA device, the proposed ISM RC-LIGBT reduces Eoff by 21.5% without snapback. Its reverse recovery charge is reduced by 53.7%/58.6% compared to that of the SSA LIGBT with Lb=40/60μm at the same Von. Due to the prominent static and dynamic characteristic, the power loss of ISM RC-LIGBT in a completed switching cycle is reduced.

Simulated Study and Surface Passivation of Lithium Fluoride-Based Electron Contact for High-Efficiency Silicon Heterojunction Solar Cells

Numerical simulation and experimental techniques were used to investigate lithium fluoride (LiFx) films as an electron extraction layer for the application of silicon heterojunction (SHJ) solar cells, with a focus on the paths toward excellent surface passivation and superior efficiency. The presence of a 7 nm thick hydrogenated intrinsic amorphous silicon (a-Si:H(i)) passivation layer along with thermally evaporated 4 nm thick LiFx resulted in outstanding passivation properties and suppresses the recombination of carriers. As a result, minority carrier lifetime (τeff) as well as implied open-circuit voltage (iVoc) reached up 933 μs and iVoc of 734 mV, accordingly at 120°C annealing temperature. A detailed simulated study was performed for the complete LiFx based SHJ solar cells to achieve superior efficiency. Optimized performance of SHJ solar cells using a LiFx layer thickness of 4 nm with energy bandgap (Eg) of 10.9 eV and the work function of 3.9 eV was shown as: Voc=745.7 mV, Jsc=38.21 mA/cm2, FF=82.17%, and =23.41%. Generally, our work offers an improved understanding of the passivation layer, electron extraction layer, and their combined effects on SHJ solar cells via simulation.

Authentication and Testing of Banknotes Using Laser Multiphoton Electron Extraction Spectroscopy (MEES)

In laser multiphoton electron extraction spectroscopy (MEES), the photo-charges extracted from a surface by a pulsed laser beam are recorded as a function of laser wavelength. We report the first application of this spectroscopy to banknotes. Various banknotes from different countries, authentic and counterfeit, have been tested. The results indicate that MEES spectra are both informative (many peaks) and reproducible. The spectra allow for clear distinction between authentic and counterfeit banknotes. Actually, MEES provides a unique fingerprint of the banknotes, so that distinction between various forgery methods (printer used) is also possible.