Function Of Gate Voltage Vg Research Articles

Impact ionization-induced bistability in CMOS transistors at cryogenic temperatures for capacitorless memory applications.

Cryogenic operation of complementary metal oxide semiconductor (CMOS) silicon transistors is crucial for quantum information science, but it brings deviations from standard transistor operation. Here, we report on sharp current jumps and stable hysteretic loops in the drain current as a function of gate voltage V G for both n- and p-type commercial-foundry 180-nm-process CMOS transistors when operated at voltages exceeding 1.3 V at cryogenic temperatures. The physical mechanism responsible for the device bistability is impact ionization charging of the transistor body, which leads to effective back-gating of the inversion channel. This mechanism is verified by independent measurements of the body potential. The hysteretic loops, which have a >107 ratio of high to low drain current states at the same V G, can be used for a compact capacitorless single-transistor memory at cryogenic temperatures with long retention times.

Effect of the Inert Gas Adsorption on the Bilayer Graphene to the Localized Electron Magnetotransport

Graphene has a fascinating property that the two-dimensional electron gas is easily accessible externally and it is challenging to investigate the effects of the adsorption of inert gases on graphene, which may be the least effective chemically and physically. We carry out the magnetotransport measurements of 4He-adsorbed bilayer graphene at low temperatures and the magnetic field B ranging from 0 to 4 T. The magnetoresistance ΔRxx change from the pristine graphene is measured as a function of gate voltage Vg and B for partial coverage of 1/10 (= 0.1) layers and one layer 4He-adsorbed graphene. The overall magnitudes of ΔRxx for one layer are larger than the one for 1/10 layers. Signs of ΔRxx depend on the Vg for the entire range of B, associated with the magnetoresistance oscillation owing to the weak localization in the pristine graphene.

Numerical study of Coulomb oscillation and phase shift through quantum dots in a magnetic field

Coulomb oscillation and phase shift are examined numerically through semiconductor quantum dots in a magnetic field. A realistic shape of the quantum dot, tunnel barriers and leads is modeled using a quasi-one-dimensional tight-binding model with smooth potential barriers. In the absence of magnetic field, we obtain a peak structure of the conductance as a function of gate voltage Vg (Coulomb oscillation) with a sequence of abrupt change of the transmission phase, so-called phase lapse. This agrees with experimental results. The magnetic field removes the phase lapse. The phase shift changes continuously, either increases or decreases by almost π with an increase in Vg, reflecting complex wavefunctions at the Fermi level.

Investigation of the non-linear input capacitance in LDMOS transistors and its contribution to IMD and phase distortion

In this paper the mechanisms causing the capacitive, reactive non-linearities in a lateral double diffused MOS, LDMOS, transistor are investigated. The non-linear input capacitance under load-line power match is extracted and analyzed. Computational TCAD load-pull is used to analyze the effect of non-linear capacitance on two-tone intermodulation distortion and AM–PM conversion in class-A operation. High-frequency measurements have been made to verify the use of 2D numerical device simulations for the analysis. It is found that the input capacitance, Cgg, of the LDMOS transistor working under power match conditions is a strongly non-linear function of gate voltage Vg but with an almost linear initial increase in Cgg. The voltage dependence of Cgg is found to mainly affect higher order IMD products in class-A operation. Transient simulations however show that Cgg seriously contributes to the onset of AM–PM conversion well below the 1dB compression point.

Transport Properties of Electrons in Inverted InSb Surface

Measurements were made of electrical transport properties of the electrons in inversion layers produced in metal–oxide–p-InSb structure at 4.2 K. One possible interpretation is reported. Surface conductance Δσs due to inversion layers as a function of gate voltage VG was measured in magnetic field H up to 14 kOe. The curves of Δσs in the magnetic field normal to the surface had plateaus. The width of the plateaus were enlarged on the positive side of VG with increasing magnetic field. While Δσs in the magnetic field normal to the surface decreased ordinarily with increasing H, Δσs in the field parallel to the surface plane tended to a finite value. Values of Δσs showed two peaks when the direction of the magnetic field was rotated in a plane normal to the surface current. The width of the peak was narrower in the case of magnetic fields where electrons were pushed toward the oxide–InSb interface rather than into the bulk of the InSb. These characteristics may be interpreted as follows: The effect of quantization of electron motion in the inversion layer becomes clearer in the behavior of Δσs with the aid of a magnetic field which quantizes the motion of electrons in planes parallel to surface. The peculiar dependence of Δσs on the direction of the magnetic field is thought to originate in the different mechanisms of electron scattering on both sides of the inversion layers mentioned above.