Channel Length Modulation Parameter Research Articles

Direct parameter extraction method of EEHEMT nonlinear model for InP HEMT

AbstractA direct parameter extraction method of EEHEMT nonlinear empirical model is proposed in this paper. An improved DC model is also presented by considering the channel length modulation parameter () as a function of gate‐to‐source voltage. Model verification is carried out by comparison of measured and simulated current–voltage characteristics and S‐parameters. Good agreement is obtained between the measured and modeled results for 2 × 15 μm gatewidth (number of gate fingers × gatewidth) 70‐nm gatelength InP high electron mobility transistors (HEMT). An increased accuracy in modeling the I–V and RF characteristics is also obtained in the proposed model, compared with the conventional one.

Analytical computation of electrical parameters in GAAQWT and CNTFET with identical configuration using NEGF method

ABSTRACTA two-dimensional quantum mechanical model is presented for calculating carrier transport in ultra-thin gate-all-around quantum wire transistor (GAAQWT) and carbon nanotube field effect transistor (CNTFET) using coupled mode space approach. Schrödinger and Poisson’s equations are self-consistently solved involving Non-Equilibrium Green’s Function (NEGF) formalism under the ballistic limit along with dissipative effects in terms of self-energy at both the source and drain ends. Effect of structural parameters on drain current, channel length modulation parameter, quantum capacitance, transconductance, subthreshold swing (SS) and drain induced barrier lowering (DIBL) are studied assuming occupancy of only a few lower sub-bands, where comparison is performed taking all other factors, biases and dimensions identical. High-k dielectric (HfO2) independently surrounding the quantum wire (GaAs) and carbon nanotube shows higher drain current and transconductance for GAAQWT but lower quantum capacitance than that obtained for CNTFET. A smaller variation of CLM for CNFET speaks in favour of it for digital quantum circuit applications, whereas GAAQWT is suitable candidate for low-power applications. Effect of structural parameters is investigated within fabrication limit to analyse the effect on electrical characteristics under lower biasing ranges.

Improved modeling method to account for the kink effect of gaas phemts

Short gate-length High Electron Mobility Transistors (HEMTs) have been observed to exhibit kinks in their drain current-voltage (I–V) characteristics. To model this nonlinear effect, we present an effective approach that is easily incorporated into most existing empirical HEMT I–V models. This has been done by modifying the channel length modulation parameter (λ) to account for the kink effect. Moreover, the definitions of the left parameters in the original model will not be influenced, and the improved HEMT I–V model enhances its bias range of operation for which accuracy is maintained. The proposed modeling method is validated through DC/ Pulsed I–V as well as large-signal power measurements.

Nonsaturating Drain Current Characteristic in Short-Channel Amorphous-Silicon Thin-Film Transistors

Nonsaturating drain current characteristics are analyzed in terms of the channel length modulation (CLM) and the self-heating effect. According to this analysis, the nonsaturating drain current arises if the effective channel length is sufficiently reduced such that the CLM effect leads to a superlinear increase of the drain current beyond saturation. The extracted CLM parameter was around ?' = 1/15 ?m/V for the samples investigated, and a nonsaturating characteristic was observed in hydrogenated-amorphous-silicon (a-Si:H) thin-film transistors (TFTs) with a channel length of 10 ?m or less. Furthermore, in a bias-temperature-stressed short-channel a-Si:H TFT, which has a laterally nonuniform threshold voltage, the experimental data showed a pronounced nonsaturating current in the reverse output characteristics and a much lower and flatter characteristic in the forwardId-Vds data. The nearly flat forward saturation characteristic is discussed in terms of the cancellation of the CLM effect by the effect from the rising threshold voltage at the pinchoff point as the drain bias increases. The pronounced nonsaturating reverse characteristic is explained in terms of the compounding effects of the rising CLM current and the rising current due to the falling threshold voltage of the pinchoff point. We also discuss a split-channel design to suppress the nonsaturating drain currents in a-Si:H TFTs.

Trade off between polysilicon film quality and thin film transistor operational amplifier DC gain

We have fabricated thin film transistor operational amplifiers on a variety of polycrystalline silicon films. We have examined the open loop DC gain of these modules, and have observed that higher quality polycrystalline silicon films usually cause a negative impact on the DC gain of the amplifier. In this paper we have attempted to quantify this relationship, presenting the gain as a function of the transistor mobility, threshold voltage and channel length modulation parameter, which collectively can describe the quality of the active film. We have found that primarily the saturation characteristics of the transistor, as represented by the channel length modulation parameter, and the device threshold voltage have the biggest impact on amplifier gain.