Research On GaN HEMT Power Device Modeling Based On Lumped-Charge Methodology

Gallium Nitride High Electron Mobility Transistor(GaN HEMT)has attracted significant attention as a new type of semiconductor device for power electronics applications due to their higher efficiency,higher temperature tolerance,and smaller size compared to traditional silicon-based power devices.In order to guide the design of GaN HEMT devices and evaluate their performance under different operating conditions,this paper focuses on the modeling of GaN HEMTs for power electronics applications and is divided into several parts:(1)Categorizing existing GaN HEMT models,analyzing their advantages and limitations,and highlighting the benefits of using lumped-charge modeling methods in GaN HEMT modeling,which include simplicity in computation,clear physical interpretations,fewer parameters,and accurate representation of multi-operating point carrier distribution.This categorization forms the basis of the modeling approach employed throughout the paper..(2)Addressing the limitations of existing empirical models,which exhibit lower accuracy under complex operating conditions and involve computationally intensive physics-based calculations.A lumped-charge model is developed for P-GaN gate GaN HEMTs.This model represents the carriers in the sub-gate channel as four lumped charges.Furthermore,an iterative solvable lumped charge network is constructed based on the current transport equation and carrier continuity equations,avoiding the need for continuous analytical solutions for the surface potential or two-dimensional electron gas(2DEG),thus simplifying the computation.The model accounts for the effects of channel length modulation and self-heating,investigates the influence of voltage on capacitance,and establishes a capacitance model.By comparing the model with experimental data,the relative errors for the static characteristics are within 5%,validating the static accuracy of the model.The relative errors for capacitance are all below 0.5%.Comparison with experimental data obtained from a dual-pulse test platform under conditions of 25°C and125°C shows relative errors in the rise and fall times of voltage and current not exceeding13%,demonstrating the model’s ability to accurately characterize the switch transient characteristics of the device under various operating conditions.(3)Addressing the limitations of existing Cascode-type GaN HEMT models,which are mostly empirical and cannot accurately represent the behavior of the internal high-voltage depletion-mode GaN HEMT devices.A lumped-charge model is used to characterize the motion of gate-substrate carriers and sub-gate charge in high-voltage depletion-mode GaN HEMTs,along with the establishment of a capacitance model.By comparing the model’s current-voltage(I-V)and capacitance-voltage(C-V)characteristics with measured data,the relative errors for I-V and C-V are within 10% and 0.4%,respectively,demonstrating the model’s accuracy in representing I-V and C-V characteristics.Furthermore,by combining this model with a Si MOSFET model,a lumped charge model accurately representing the static and switch transient characteristics of Cascode-type GaN HEMTs is established.By comparing the model with measured results,the static and switch transient characteristics of the model demonstrate high accuracy under different operating conditions.