Investigation of the impact of the GaN Cap Layer on DC and RF performance in N-Polar AlGaN/GaN HEMTs

Chumki Das Kaushik Mazumdar ^*

• Indian Institute of Technology Dhanbad, Dhanbad, India

In this paper, we investigated the logic and RF performance of nanostructure N-polar AlGaN/GaN high-electron mobility transistors (HEMTs) with and without a GaN cap layer. It's found that devices without the GaN cap layer exhibit superior performance, the maximum drain current density of 0.99 mA/µm at VGS = 2 V and a corresponding on-state resistance (Ron) of 0.88 Ω•mm. The GaN HEMT without GaN cap layer leads to a peak transconductance of 0.75 S/mm at VDS = 3 V. Varying the drain doping concentration significantly affects both the current density and transconductance. At a doping concentration (ND) of 10 22 cm⁻³, the device without GaN cap layer achieves a maximum current density of 0.98 mA/µm at VDS = 1 V, and the maximum cutoff frequency (fT) of 183.8 GHz at VDS = 3 V. These findings highlight the potential of N polar AlGaN/GaN HEMTs without the GaN cap layer for high-power, high-frequency, and micro-and nano-electromechanical system (M/NEMS) sensors applications.