Threshold Voltage Vt Research Articles

塑性変形におけるAEの振幅分布

The amplitude distribution of acoustic emission due to plastic deformation was studied in relation to deformation properties of Al, Cu, Al-Mg, Al-Si, α-Brass, α-Fe and SUS 304. The integrated distribution function of AE amplitudes can be given by(This article is not displayable. Please see full text pdf.) \ oindentwhere I(Vt) shows the cumulative number of ringdown countings, whose amplitude are equal to or greater than a given threshold voltage Vt, m and k are constants defined as the threshold exponent and the threshold pre-exponent respectively. The threshold exponents may be classified to three categories: 0.5, 1 and 2, respectively. The case of m=2, which represents Gaussian distribution, was observed in high purity Cu and Al, and corresponds to the so-called continuous-type of AE. The case of m=0.5, on the other hand, corresponds to the burst-type of AE and was observed in SUS 304 and Al-Si alloy. The case of m=1 shows the mixture mode of continuous and burst-type of AE, and was observed in Al-Mg, α-Brass and α-Fe.These threshold exponent m values are strongly connected with the metallurgical factors, which control the flow deformation, such as Peierls potential, solute atoms, dispersion particles, and stacking fault energy. The variation of m values between 0.5 and 2.0 can be explained by simple AE models, characterized by the terms of stress concentration and the frictional stress.The stress concentration (elastic stored energy) controls the magnitude of discontinuos deformation. The frictional stress controls the relaxation rate of the energy release.

Implant dose profile dependence of electrical characteristics of ion-implanted MOS transistors

Ion-implanted MOS transistors were fabricated and their electrical characteristics, such as threshold voltage, effective mobility, etc., were measured. In the 11B+-implanted p-channel case, threshold voltage VT can be shifted linearly with implant dose. These shifts ΔVT were entirely determined by the net dose entering silicon. On the other hand, in the 11B+-implanted n-channel case, threshold voltage shift ΔVT varied sublinearly with dose and showed strong dose profile dependence. The profiles were varied with changing implantation energies and annealing times. These results can be interpreted in accordance with the rapid decrease of the maximum surface depletion layer Xd max with the implant dose increase. Numerical calculations of threshold voltage shifts accounting for nonuniformly implanted profiles were compared with observed results. Good agreement was obtained. Effective mobilities μeff of 11B+-implanted p - and n -channel MOS transistors also showed different dose dependences. In the low-dose region, effective mobilities of 11B+-implanted p -channel MOSFET remained almost unchanged, but those of the n -channel case decreased monotonically with dose increase. Qualitative arguments, taking into account surface scattering and impurity scattering effects, and rough calculations are presented.

Threshold-voltage sensitivity of ion-implanted m.o.s. transistors due to process variations

Adjustment of the threshold voltage VT by ion implantation yields a certain distribution of threshold voltages determined by different process parameters. A procedure is presented for minimising the threshold-voltage sensitivity of implanted m.o.s. transistors due to these parameters for a typical set of process parameters.

Bistable noise in p-n junctions : S. T. Hsu. Solid State Electron.14 (1971), p. 487

We experimentally investigate the large-signal radio frequency performances of surface-channel p-type diamond MESFETs fabricated on hydrogenated polycrystalline diamond. The devices under examination have a coplanar layout with two gate fingers, total gate periphery of 100 μm; in DC they exhibit a hole accumulation behavior with threshold voltage Vt ≈ 0–0.5 V and maximum drain current density of 120 mA/mm. The best small-signal radio frequency performances (maximum cutoff or transition frequency fT and oscillation frequency fmax) were obtained close to the threshold and were of the order of 6 and 15 GHz, respectively. The power radio frequency response was characterized by driving the devices in class A at an operating frequency of 2 GHz and identifying through the active load-pull technique the optimum load for maximum power added efficiency. A power gain in linearity of 8 dB and an output power of approximately 0.2 W/mm with 22% power added efficiency were obtained on the optimum load impedance at a bias point VDS = −14 V, VGS = −1 V. To the best of our knowledge, these are the first large signal measurements ever reported for surface MESFET on polycrystalline diamond, and show the potential of such technology for the development of microwave power devices.

Gate Controlled Si PIN-Structure

Si pin-diodes with nearly intrinsic region have negative resistance in the forward direction when the ratio W/L is 6–12, where W is the width of i-region and L the ambipolar diffusion length. The threshold voltage VT for giving the negative resistance varies in the wide range from 1 to 200 V, strongly depending on the ratio W/L. It is found that the threshold voltage VT can be decreased by a gate on the i-region. The necessary condition to turn on the diode is that the gate current IG increases up to a threshold current IT for giving the negative resistance. By observing the transient behaviour of the gate current, two processes are found to occur succeedingly in the turn-on process. The first process is the increase of current due to the injection of carriers up to the threshold current acting as a trigger to turn on the diode. The second process brings whole the i-region to negative resistance by filling up the recombination centers from cathode to anode.