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In this article, we report the development of a novel physics-based analytical model for explaining the current–voltage relationship in Schottky barrier (SB) 2-D-material field effect transistors (FETs). The model has at its core the calculation of the surface-potential (SP) which is accomplished by invoking 2-D density of states in conjunction with Fermi–Dirac (FD) distribution for electron and hole statistics. The explicit computation for the SP, carried out using the Lambert-W function together with Halley’s method, is used to construct the SP-based band-diagram for realizing the transparency of the SBs. Thereafter, the ambipolar current is derived in terms of the electron and hole injection phenomena—the thermionic emission and Fowler–Nordheim tunneling mechanisms—at the SB contacts. Furthermore, drift-diffusion current is derived in terms of the SP and incorporated in the model to account for the scattering in the intrinsic 2-D channel. Finally, the Verilog-A model is validated against experimental ${I}-{V}$ data reported in the literature for two different 2-D-material systems. This is the first demonstration of an explicit SP-based SPICE model for ambipolar SB-2-D-FETs that is simultaneously built on tunneling-emission and drift-diffusion formalisms.

We report a charge-based analytic and explicit compact model for field effect transistors (FETs) based on two-dimensional materials (2DMs), for the simulation of 2DM- based analog and digital circuits. The device electrostatics is handled by invoking 2D density of states and Fermi-Dirac statistics, that are later combined with Lambert-W function and Halley’s correction, so to eventually obtain explicit expressions for the electron and hole charges, which are exploited in the calculation of drift-diffusion currents for both carriers. Further, the charge model is extended to obtain characteristics of 2DM- based negative capacitance FETs. The model is benchmarked against experimental MoS2 FET measurements, and experi- mental ambipolar characteristics of narrow band-gap materials such as black phophorous. Its soundness for SPICE circuit-level simulations is also demonstrated.

We present the latest developments in Advance SPICE Model for GaN (ASM GaN) HEMTs in this paper. The ASM GaN model has been recently selected as an industry-standard compact model for GaN radio frequency (RF) and power devices. The core surface-potential calculation and the modeling of real device effects in this model are presented. We discuss the details of the nonlinear access region model and enhancement in this model to include a physical dependence on barrier thickness. We also present the novel model feature of configurable field-plate modeling and discuss the extraction procedure for the same. New results with the ASM GaN model on high-frequency and enhancement-mode GaN power devices are also presented.

In this paper, a consistent DC to RF modeling solution for Al gallium nitride (GaN)/GaN high electron mobility transistors is demonstrated that is constructed around a surface-potential-based core. Expressions for drain current and intrinsic terminal charges in the form of surface-potential are used to simultaneously model the DC characteristics and the intrinsic capacitances of a commercial GaN device. Self-heating and trapping effects are incorporated to account for the non-linear nature of the device. We discuss the parameter extraction flow for some of the key model parameters that are instrumental in fitting the DC characteristics, which simultaneously determines the bias-dependent intrinsic capacitances and conductances that significantly eases the RF parameter extraction. Parasitic capacitances, gate finger resistance, and extrinsic bus-inductances are extracted, from a single set of measured non-cold-FET S-parameters, using the model process design kit. The extraction procedure is validated through overlays of broadband (0.5-50 GHz) S-parameters, load-pull and harmonic-balance (10 GHz) simulations against measured data, under multiple bias conditions to successfully demonstrate the model performance at large-signal RF excitations.

In this paper, we present a capacitance model for field-plate AlGaN/GaN High Electron Mobility Transistor (HEMTs) accounting for the contribution of substrate capacitances and cross-coupling between field plates. TCAD simulations are performed to analyze both these contributions and analytical expressions for charges corresponding to the cross-coupling and substrate capacitances are presented in terms of our existing surface-potential-based model. The modeled results are validated by comparing the time-domain waveforms of a test circuit using a mixed-mode simulation setup in which the impact of cross-coupling and substrate capacitances on accuracy of switching transients predicted by the model is discussed.

In this letter, we propose a method to extract the small-signal equivalent circuit model for GaN HEMTs using extrinsic-level RF broadband (0.5–50 GHz) Z-parameters. The measured Z-parameters of large gate-periphery GaN devices exhibit certain interesting characteristics, due to their inherently larger intrinsic capacitances and their subsequent interaction with the extrinsic inductances. We exploit these characteristics to simultaneously extract the intrinsic as well as the extrinsic small-signal model components and successfully validate it with measured S-parameter data for a $10~\times90~\mu \text{m}$ GaN device.

In this letter, we present a novel approach toward understanding the Kink effect (KE) in the bode plot of short circuit current gain ( ${h_{21}}$ ) observed for microwave transistors, particularly gallium nitride (GaN) HEMTs. We ascribe the origin of the KE to the presence of a pair of complex conjugate poles at the frequency of interest, introduced due to the extrinsic parasitic inductances and their interaction with the device intrinsic elements, such as the capacitances and transconductance, and develop simplified mathematical expressions that govern the behavior of the kink. We also present a physics-based compact model that is capable of capturing the KE and extensively validate the model against measured data for a GaN device under multibias conditions, thereby advocating the strong physical background of the model. We conclude by demonstrating the impact of various elements of the small signal model on the kink based on the developed mathematical hypothesis for KE.

In this paper, the impact of source via-inductance on stability performance of large gate-periphery RF transistors is investigated in terms of Rollett’s stability factor (K-factor) using a small-signal equivalent circuit model. The RF device-under-test studied in this work is a commercial multi-finger GaN HEMT with a considerably large gate-periphery of 10 × 90 µm. A systematic analysis of the K-factor is done by deriving its mathematical expression in terms of the equivalent circuit intrinsic and extrinsic components. While gate-to-drain capacitance is unanimously considered to be the most critical component in determining the device stability performance, due to the formation of the feedback loop, the simulation and experimental results obtained in this work reveal potential regions of device instability in the form of peaks and valleys, that emerge as a manifestation of the coupling between the via-inductance and the intrinsic drain-to-source capacitance. This study is of significance particularly to multi-finger large gate-periphery devices since they have a reduced gate-resistance and therefore are driven further into instability. This work is expected to serve as a guideline in obtaining optimized multi-finger RF transistors with regard to stability.

In this paper, we present a physics based compact model for GaN-based Metal-Semiconductor-Metal (MSM) 2DEG varactors in which the intrinsic charges and currents are evaluated in terms of the bias-dependent surface-potential. Physical phenomena such as Thermionic Emission, Poole-Frenkel Effect and Fowler-Nordheim Tunneling are incorporated to realize the non-idealities of the Schottky gates. The model is successfully validated against measured data for a state-of-the-art GaN-based varactor. Furthermore, a circuit simulation is performed for a phase shifting network wherein its behavior for various bias conditions and operating frequencies is observed using the proposed model.

In this paper, a surface-potential-based compact model is proposed for the capacitance of an AlGaN/GaN high-electron mobility transistor (HEMT) dual field-plate (FP) structure, i.e., with gate and source FPs. FP incorporation in a HEMT gives an improvement in terms of enhanced breakdown voltage, reduced gate leakage, and so on, but it affects the capacitive nature of the device, particularly by bringing into existence in a subthreshold region of operation, a feedback miller capacitance between the gate and the drain, and also a capacitance between the drain and the source, therefore, affecting switching characteristics. Here, we model the bias dependence of the terminal capacitances, wherein the expressions developed for intrinsic charges required for capacitance derivation are analytical and physics-based in nature and valid for all regions of device operation. The proposed model, implemented in Verilog-A, is in excellent agreement with the measured data for different temperatures.