Generalized Frequency Dependent Small Signal Model for High Frequency Analysis of AlGaN/GaN MOS-HEMTs

Aakash Jadhav,Joel T Asubar,Masaaki Kuzuhara,Hiroshi Amano,Manato Deki,Biplab Sarkar,Ali Baratov,Takashi Ozawa,Sourajeet Roy,Shunpei Yamashita,Akio Wakejima,Yoshio Honda

doi:10.1109/jeds.2021.3081463

Abstract

Traditional lumped small signal equivalent circuit models of AlGaN/GaN metal oxide semiconductor high electron mobility transistors (MOS-HEMTs) are made up of constant valued circuit elements. Such models are unable to capture the high frequency behavior (above 20 GHz) of the device. In this work, a modified small signal equivalent circuit model of AlGaN/GaN MOS-HEMTs is presented. The key feature of the proposed model is that the values of the different circuit elements in the model are considered to be frequency dependent in nature and not constants. The frequency dependent value of each circuit element is mathematically represented using polynomial functions where the coefficients of the functions are determined via a least-square curve fitting approach. This frequency dependent attribute of the circuit element values ensures that the proposed model is very accurate at high frequencies without sacrificing the compactness of the model topology. The accuracy of the proposed model has been verified up to 50 GHz using experimentally measured Y-parameters of AlGaN/GaN MOS-HEMTs having a different gate dielectric and gate length.

Highlights

AlGaN/GaN high electron mobility transistors (HEMTs) are potential candidate devices to construct radio frequency (RF) electronic circuits for future 5G communications, defense, and space applications [1], [2]
We present a modified small signal equivalent circuit (SSEC) model of AlGaN/GaN MOS-HEMTs that is, by construction, significantly more accurate over the high frequency region of operation
The ability of the proposed frequency dependent SSEC model to directly utilize the equation (2) in order to predict the Y-parameters of the AlGaN/GaN MOS-HEMT device represent a clear advantage over the reported works of [14], [18]–[21]

Summary

INTRODUCTION

AlGaN/GaN high electron mobility transistors (HEMTs) are potential candidate devices to construct radio frequency (RF) electronic circuits for future 5G communications, defense, and space applications [1], [2]. The proposed model is validated using measured Y-parameter data for two different gate dielectrics and gate length values for AlGaN/GaN MOS-HEMT devices. A similar observation is reported by Ahsan et al where conventional constant value SSEC models of AlGaN/GaN HEMTs correctly predict the measured Y-parameters at low-frequency whereas inductive effects dominating at high frequency results in failure of the same models [13]. Adding these additional inductive circuit elements lead to greater model accuracy, but at the cost of greater model complexity.

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RESULTS AND DISCUSSION

CONCLUSION