Co-Optimized E-Mode AlGaN/GaN HEMT with Composite P-GaN Recessed Cap and Etched Doped Buffer for Simultaneous DC and RF Performance Enhancement

Abstract

This study presents a theoretical analysis of the DC and RF characteristics of enhancement mode (E-mode) AlGaN/GaN High Electron Mobility Transistor (HEMT) utilizing symbiotic integration of advanced techniques e.g. composite gate structure with slightly etched buffer. Enhancement-mode (Emode) GaN HEMTs often face a fundamental trade-off: achieving high positive threshold voltage (Vth) typically degrades RF metrics such as lower cut-off frequency (f_T) and deteriorated transconductance (g_m). To overcome these issues with practical implications, this expedite structure is introduced. The performance analysis is done using TCAD ATHENA to etch, doped, diffusion, and deposition of the architecture as well as TCAD ATLAS to characterize the DC and RF performance. Conventional methods solely focus on individual techniques such as P-GaN caps, recessed gate, buffer etching or doping. This work proposes a synergistically engineered E-mode AlGaN/GaN HEMT which combines these key features: (1) a P-GaN cap, (2) a recessed gate structure, and (3) a slightly etched and carbon-doped AlGaN buffer layer. This combined implementation is only reported in this paper. The device achieves a V_th of 2.43 V with higher g_m around 325 mS/mm. This ensures the device remains off at normal secure condition with better gate control characteristics. The lower on-resistance of 139.4 mΩ indicates it can conduct more current for a given gate voltage, reducing power loss when the device is on. This architecture also attains a breakdown voltage (V_br) around 1103 V which points out a better threshold performance metrics. Under small signal analysis at 1 MHz, key findings have achieved include maximum current of 630 mA/mm, a cut-off frequency of approximately 40 GHz. This simultaneous optimization of DC and RF metrics addresses limitations of prior E-mode designs and makes the device suitable for advanced RF and microwave applications.