Improved breakdown voltage mechanism in AlGaN/GaN HEMT for RF/Microwave applications: Design and physical insights of dual field plate

Abstract

This work investigated and proposed the source–gate dual field plate (SG-FP) AlGaN/GaN HEMT for different gate-to-drain drift distances with a fixed gate length of 0.25 μm using ATLAS-TCAD. The increment in the GaN buffer thickness and gate-to-drain drift distance with the variation in the field plate length improves the device performance and breakdown voltages by maintaining the impact ionization mechanism. The breakdown voltage behavior, physical insights of electric field contour, impact generation rate, and potential profile intricacies of source field plate (S-FP), gate field plate (G-FP), and dual field plate (SG-FP) are illustrated. The proposed source–gate dual field plate (SG-FP) with the SiN passivation interfacial layer, SiO2, thicker GaN buffer, and extended gate-to-source drift region is best suited for optimal performance in high breakdown voltage, with optimum cut-off frequency and low gate-leakage current. The proposed dual field plate AlGaN/GaN device with the source field plate (LS-FP = 4 μm), gate field plate (LG-FP = 2 μm), the AlGaN buffer thickness of 3.697 μm, and gate-to-drain drift distance of 8 μm show the highest breakdown voltage of 562 V with the optimum frequency of 8.861 GHz. Finally, the AC/DC characteristics of the optimized dual field plate (SG-FP) are demonstrated. We observed that the source–gate dual field plate (SG-FP) device shows a 6.70% and 4.09% improvement in breakdown voltage compared to individual source field plate (S-FP) and gate field plate (G-FP) designs, respectively. This work shows that the proposed dual field plate device is used in power switching, high-power, and RF/Microwave applications due to its superior breakdown voltage performance, reduction in parasitic capacitances, and optimal cut-off frequency.