GaN-Based Multi-Channel Transistors with Lateral Gate for Linear and Efficient Millimeter-Wave Power Amplifiers

Abstract

We report on GaN-based field effect transistors with laterally-gated multiple 2DEG channels, called BRIDGE FETs (buried dual gate FETs). Unique operation principle of the transistors demonstrated unprecedented device characteristics suitable for efficient and linear millimeter-wave power amplifier applications. Multiple 2DEG channels formed in AlGaN/GaN and AlN/GaN material systems are compatible with the BRIDE FET structure, adding design flexibility for an increased drain current density with higher frequency performance. The BRIDGE FET fabricated on a 4-channel epi structure with a net 2DEG density of 1.2×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">13</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> exhibited 1.7× higher saturation current density than those on a single-channel with the same 2DEG density. This is attributed to a higher saturation velocity of 2DEG with a lower density per channel. Finally, hexagonal micro-scale device cells consisting of segmented BRIDGE FETs construct a power amplifier (PA) unit cell, where distributing heat sources uniformly over an entire PA cell area maximizes its area power density while minimizing a rise of the peak junction temperature.