Large Signal Response of AlN/GaN/AlN HEMTs at 30 GHz

Abstract

Power amplifier (PA) technology is essential to the future of millimeter-wave (mm-wave) communication systems in defense and commercial sectors. High atmospheric attenuation at these mm-wave frequencies has led to demand for high power PAs able to offset this effect. Gallium nitride high-electron-mobility-transistors (GaN HEMTs) have emerged as leading contenders to supply high power at mm-wave frequencies due to its wide bandgap and high electron velocity. To improve upon conventional GaN HEMT heterostructures, we previously introduced HEMTs on the aluminum nitride (AlN) platform [1] , using an AlN/GaN/AlN heterostructure. The maximized bandgap of binary AlN prevents buffer leakage current and increases HEMT breakdown voltage, while also providing a higher thermal conductivity for enhanced channel temperature management. Additionally, the increased polarization offset with GaN allows for highly scaled top barriers that still induce large density two-dimensional electron gases (2DEGs). We recently showed high breakdown voltage of up to 2 MV/cm in RF AlN/GaN/AlN HEMTs [2] and RF power operation of these HEMTs at 6 GHz, with an power added efficiency of 55% and output power (P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">out</sub> ) of 2.8 W/mm [3] . In this work, we demonstrate the first mm-wave frequency operation of AlN/GaN/AlN HEMTs, showing a peak PAE = 29%, with associated P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">out </sub> = 2.5 W/mm and G <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> = 7 dB at 30 GHz.