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In this article, we present a surface-potential-based approach to model the bias-dependent effective velocity observed in AlGaN/GaN high-electron-mobility transistors (HEMTs) due to optical phonon scattering. Our model precisely reproduces the progressive decrease in the saturation velocity in GaN HEMTs with increasing gate voltages, as reported in the literature, which is predominantly due to the scattering of electrons, forming the high-density two-dimensional electron gas (2DEG), by optical phonons at high overdrive voltages. We show that this dependence differs from the traditional mobility degradation models in terms of its impact on the device current–voltage ( ${I}$ – ${V}$ ) characteristics and illustrate how the inclusion of a velocity saturation model also provides the model users with an additional handle for parameter extraction. The model is explicit and, by virtue of its Simulation Program with Integrated Circuit Emphasis (SPICE) compatibility, is readily implemented in the industry-standard Advanced SPICE Model for HEMTs (ASM-HEMTs) model and has been validated against experimental dc ${I}$ – ${V}$ and RF S-parameter measurements of an in-house GaN device.

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 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 we present the dependence of Gallium nitride (GaN) high electron mobility transistor (HEMT) AM/AM and AM/PM non-linearities on AlGaN barrier layer thickness (Tbar). While the effect of barrier layer thickness on two-dimensional electron gas density has been shown earlier, in this paper we show for the first time that Tbar affects the non-linear behavior of the device through the changes in channel effective mobility and capacitances. We accurately model five different GaN HEMT devices with Tbar varying from 8 nm to 25 nm using a physics-based model and use the developed accurate model as a tool to analyze the non-linear behavior of the GaN HEMT device.

In this paper, we aim to present a surface potential based model for GaN High Electron Mobility Transistors. The analytical model is computationally efficient and can be accurately used for DC and RF predictions. It includes various effects of velocity saturation, access region resistance, temperature, gate current and noise.

In this work, we study the trapping in GaN power HEMTs and discuss effect of traps on device characteristics. Simulation setups for analysis of switching collapse and current collapse observed in pulsed I–V are also presented. We propose an RC network based trap model to capture the effect of trapping in a surface potential based compact model for GaN HEMTs. The proposed model has been verified with the hardware data for various quiescent biases and frequencies, and the model results are in excellent agreement with the hardware data.

Incorporation of Field Plate in High Electron Mobility Transistors (HEMTs) improves the device breakdown voltage but on the other hand, increases the device Capacitance. It has a direct impact on the device switching characteristics and hence the study of the capacitive behavior holds supreme importance for GaN HEMTs power switching application. Also, in GaN HEMTs, lower values of access region resistance improves the device output current but at the cost of increase in its capacitance, C GD . In this paper, using TCAD simulations on a field plated GaN HEMT, we present the physical explanation for the variation in C-V characteristics for different access region and field plate lengths.