Deep-ultraviolet (DUV) solar-blind photodetectors based on high-quality cubic boron nitride (cBN) films with a metal/semiconductor/metal configuration were fabricated. The design of interdigitated circular electrodes enables high homogeneity of electric field between pads. The DUV photodetectors present a peak responsivity at 180nm with a very sharp cutoff wavelength at 193nm and a visible rejection ratio (180 versus 250nm) of more than four orders of magnitude. The characteristics of the photodetectors present extremely low dark current, high breakdown voltage, and high responsivity, suggesting that cBN films are very promising for DUV sensing.
A detailed analysis of nonequilibrium electron transport in n-type Si and In 0 .3 Ga 0 .7 As MOSFETs scaled into ultimate limit of 5-nm gate length is carried out using ensemble Monte Carlo device simulations. The analysis is based on simulations of I D -V G characteristics for a template, 25-nm gate length Si MOSFET compared against previous results from various Monte Carlo device codes, and for an equivalent 25-nm gate length In 0 .3 Ga 0 .7 As MOSFET. The transistors are then laterally scaled from a gate length of 25 nm to 20, 15, 10 and 5 nm monitoring the average electron velocity, energy, and sheet density along the channel at a supply voltage of 1.0 V. A degradation of the injection velocity with the scaling of a gate/channel length is observed. While we have found a decrease in the overall electron velocity profile along the Si channel for gate lengths smaller than 10 nm and a decrease in the injection velocity from a gate length of 20 nm, the increase in the intrinsic drain current in the scaling process is continuous thanks to the increasing velocity at the drain side. However, the velocity in the InGaAs channel MOSFETs increases steadily during the scaling but the increase in the intrinsic drain current is less pronounced. This is the result of a source starvation, due to a low density of states in III-V semiconductors, which cannot provide a large enough electron sheet density in the channel. This effect is partially mitigated by the enhancement of density of states as a proportion of electrons in the source/drain transfers to upper valleys with a larger electron effective mass.
Deep-ultraviolet solar-blind photodiodes based on high-quality AlN films grown on sapphire substrates with a metal-semiconductor-metal configuration were simulated and fabricated. The Schottky contact is based on TiN metallisation. The material is characterised by micro-Raman spectroscopy and X-ray diffraction technique. The detector presents extremely low dark current of 100fA at -100V DC bias for a device area of 3.1 mm 2 . It also exhibits a rejection ratio between 180nm and 300nm of three orders of magnitude with a very sharp cut-off wavelength at 203nm (∼6.1eV).The simulation, based on a 2D energy-balance model using COMSOL® software, permits to help the designer for the optimum topology determination by means of physical studies. The measurement results are in good agreement with the model predictions.
The interplay of self-heating and polarization affecting resistance is studied in AlGaN/GaN Transmission Line Model (TLM) heterostructures with a scaled source-to-drain distance. The study is based on meticulously calibrated TCAD simulations against I-V experimental data using an electrothermal model. The electro-thermal simulations show hot-spots (with peak temperature in a range of ∼ 566 K -373 K) at the edge of the drain contact due to a large electric field. The electrical stress on Ohmic contacts reduces the total polarization, leading to the inverse/converse piezoelectric effect. This inverse effect decreases the polarization by 7 %, 10 %, and 17 % during a scaling of the source-to-drain distance in the 12 µm, 8 µm and 4 µm TLM heterostructures, respectively, when compared to the largest 18 µm heterostructure.
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