Abstract

Monolithic GaN High Electron Mobility Transistor (HEMT)-integrated circuits are a promising application of wide band-gap materials. To date, most GaN-based devices behave as NMOS-like transistors. As only NMOS GaN HEMT is currently commercially available, its control circuit requires special design if monolithic integration is desired. This article analyzes the schematics of a GaN-based comparator, and three comparator structures are compared through ADS simulation. The optimal structure with the bootstrapped technique is fabricated based on AlGaN/GaN Metal–Insulator–Semiconductor (MIS) HEMT with the recessed gate method. The comparator has excellent static characteristics when the reference voltage increases from 3 V to 8 V. Dynamic waveforms from 10 kHz to 1 MHz are also obtained. High-temperature tests from 25 °C to 250 °C are applied upon both DC and AC characteristics. The mechanisms of instability issues are explained under dynamic working condition. The results prove that the comparator can be used in the state-of-art mixed-signal circuits, demonstrating the potential for the monolithic all-GaN integrated circuits.

Highlights

  • GaN-based power devices have shown superior performances in communication systems and power conversion to Si-based devices, especially in high-speed, high power, and high-temperature applications

  • In order to reduce the physical size of the modules and parasitic parameters to show the superiority of the material, the monolithic integrated circuits on GaN epitaxial wafers have undergone extensive research in the last 20 years

  • Regarding the circuit-level stability test, the impact of threshold instability for the Direct Coupled FET Logic (DCFL) inverter was reported for the first time in 2021 [17], while the comparator suffers from the same limitations that may cause fault

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Summary

Introduction

GaN-based power devices have shown superior performances in communication systems and power conversion to Si-based devices, especially in high-speed, high power, and high-temperature applications. In 2018, monolithic logic circuits including NOT, NAND and NOR were reported because of their large noise margin and high-temperature performances [8]. Regarding the circuit-level stability test, the impact of threshold instability for the DCFL inverter was reported for the first time in 2021 [17], while the comparator suffers from the same limitations that may cause fault. This article focuses on the circuit-level hightemperature stability of the monolithic AlGaN/GaN MIS-HEMT-integrated comparator. The static and dynamic results under 250 °C environments are presented to explore how the high-temperature conditions affect the circuit stability. This comparator indicates the advantages of the integrated circuits for high-temperature applications and provides additional directions for future design

Circuit Simulation
Device Fabrication
Results and Discussion
Conclusions

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