High-Performance GaN MOSHEMTs Fabricated With ALD Al2O3Dielectric and NBE Gate Recess Technology for High Frequency Power Applications

Abstract

High-performance GaN metal–oxide–semi-conductor high-electron-mobility transistors (MOSHEMTs) using Al2O3 gate dielectric deposited by atomic layer deposition (ALD) and damage-free neutral beam etch (NBE) gate recess process for millimeter-wave power applications are demonstrated. The high-quality ALD Al2O3 reduces the gate leakage current of the device and the NBE method eliminates the plasma-induced defects in the nitride materials. The MOSHEMT device fabricated exhibits a high maximum drain current density ( ${I}_{\textsf {DS,max}}$ ) of 1.65 A/mm and a high peak extrinsic transconductance ( ${g}_{\textsf {m.ext}}$ ) of 653 mS/mm. The MOSHEMT device also demonstrates excellent RF performances, including ${f}_{T}/{f}_{\textsf {MAX}}= 183$ /191 GHz, NF $_{\textsf {min}}= 2.56$ dB with ${G}_{\textsf {AS}}= 5.61$ dB at 54 GHz, and an output power density of 2.7 W/mm associated with a power-added efficiency of 20.9% and a linear power gain of 9.4 dB at 38 GHz. To the best of our knowledge, the noise performance at 54 GHz is the best reported so far for the AlGaN/GaN HEMTs.