HEMT With Ultralow Contact Resistance by Room Temperature Process With One-Step EBL T-Shape Gates for Subterahertz Applications: Design, Fabrication, and Characterization

We present the design, fabrication, and characterization of InGaAs channel high electron mobility transistors (HEMTs) with ultralow contact resistance for millimeter-wave and subterahertz applications. The HEMT has a composite InGaAs channel and a 50-nm T-shaped gate, which was realized through a single-step electron beam lithography (EBL) process. A room temperature ohmic contact fabrication process achieving the lowest contact resistance of 15 m<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega \cdot $ </tex-math></inline-formula> mm has been developed with all room temperature process. The I–V measurements of the HEMTs at room temperature revealed a peak drain current of 0.75 A/mm and a transconductance of 1.4 S/mm. In standard 50-<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega ~{S}$ </tex-math></inline-formula>-parameter measurements, the HEMTs exhibited a maximum gain of 10 dB at 170 GHz. However, utilizing an active load-pull measurement, the 50-nm HEMT shows a gain of 14.5 dB at 170 GHz and 2 dB at 270 GHz. The load-pull measurements also obtained power added efficiency (PAE) and 1-dB compression point of the HEMTs. The noise performance was characterized using a noise parameter system with source tuner between 2 and 50 GHz. A drift-diffusion model was used to benchmark the dc and RF performance of the devices, and good agreements have been achieved.