N-polar deep recess AlGaN/GaN HEMTs with AlGaN gate capping to mitigate dispersion without field plates and enhance breakdown fabricated on SiC substrates
Abstract
Short Work Statement: Funds are provided to develop Nitrogen polar Gallium Nitride (GaN)-based High Electron Mobility Transistors (HEMT) for RF applications. The PI is Prof. Umesh Mishra, the performer is the University of California, Santa Barbara.This is a 3-year grant totaling $850,000. The grant is partially funded ($250K in FY15) with DARPA funding.A deep gate recess HEMT approach will be pursued to overcome limitations in standard field plate technology hampering the performance of devices operating at frequencies above 30 GHz. This effort will focus on Nitrogen-polar epitaxial films synthesized on SiC substrates. In addition deep recess devices with modified designs will be investigated. The baseline material will be grown by MOCVD on miscut C-face SiC substrates. Comparison structures on N-polar materials grown on on-axis C-face SiC by MBE will be also investigated. The devices will be characterized for their DC performance and AC/DC dispersion down to 200 nS. Device breakdown will be measured using the Drain Current Injection technique. Device gate lengths ranging from 700 nm down to 80 nm will be fabricated. The devices will be tested for their small signal RF performance, and large signal performance using load pull at both 30GHz and at 94 GHZ. Progress Statement: New Start FY15ApproachA deep gate recess HEMT approach will be pursued to overcome limitations observed in standard field plate technology with conventional surface passivations, where problems with dispersion have been observed. This effort will focus on Nitrogen-polar epitaxial films synthesized on SiC substrates. In addition deep recess devices with modified designs will be investigated. The baseline material will be grown by MOCVD on miscut C-face SiC substrates. Comparison structures on N-polar materials grown on on-axis C-face SiC by MBE will be also investigated. The devices will be characterized for their DC performance and AC/DC dispersion down to 200 nS. Device breakdown will be measured using the Drain Current Injection technique. Device gate lengths ranging from 700 nm down to 80 nm will be fabricated. The devices will be tested for their small signal RF performance, and large signal performance using load pull at both 30GHz and at 94 GHZ. Objective The objective of this effort is to demonstrate Nitrogen-Polar millimeter-wave HEMT s with superior power-added efficiency (PAE) as compared with Ga-polar technology.Overall Merit and ONR Mission / RelevanceHigh PAE is a key challenge for many mm-wave transmitters, as low efficiency leads to reduced time on station, increased SWaP to handle cooling requirements, and severely impacts affordable platform acquisition costs. Initial basic research results suggest that Nitrogen Polar HEMT s will significantly increase transmitter PAE as compared to current Ga-polar technology.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jan 25, 2017
- Source ID
- N000141512084
Entities
People
- Umesh Mishra
Organizations
- Office of Naval Research
- United States Navy
- University of California, Santa Barbara