Ultra-scaled channel N-polar GaN High Electron Mobility Transistors on on-axis GaN and SiC substrates for Next Generation of Wireless Technology
Abstract
This proposal aims to develop the science and technology to enable high-frequency high-power GaN-based transistors for the next generation of wireless technology. It is clear that generations beyond 5G will continue to operate at higher frequencies, demanding higher gain and efficiency. There is also a need for efficient solid-state power amplification to replace complex, low efficiency multi-stage circuits and bulky and fragile vacuum tubes in defense applications.Additionally, in the era of internet of things (IoT), artificial intelligence and autonomous vehicles, there is an urgent need for high-power and high frequency transistors that can facilitate ultra-fast, highly reliable, and low latency wireless networks. To serve these needs, transistors which can provide a combination of high power density and high efficiency at high frequencies are required. To accomplish this goal, a novel approach is proposed which enables aggressive scaling of gate length and gate-to-channel distance while maintaining a channel with high electron mobility, high electron velocity and high charge density.In this project, we propose to aggressively reduce the channel thickness to 3 nm in N-polar GaN HEMT structures. For this purpose, N-polar GaN HEMTs with InAlN as the backbarrier on onaxis GaN and SiC substrates will be developed via plasma-assisted molecular beam epitaxy (PAMBE). The usage of InAlN as the barrier instead of AlGaN, which is commonly used in traditional HEMTs, is to maintain high charge density in the channel while scaling down the channel thickness. We will study the electron transport in HEMT structures with InAlN backbarrier and identify the impact of scaling the channel on charge density and electron mobility. We will then modify the barrier by changing InAlN thickness, and/or doping profile to increase charge density and improve electron mobility in the ultra-thin channels. We will fabricate ultra-thinchannel HEMTs using two different methods (1) on epi-structures with ultra-thin GaN channel (2) recessed gate on epi-structures with 20 nm GaN channel. PAMBE will allow us to grow N-polar HEMT structures on on-axis substrates, which is not possible by MOCVD.The significant goals of this proposal are as following: Development of thin N-polar GaN films (~200 nm) with medium dislocation density (~ 108 cm-2) on on-axis C-face SiC via plasma-assisted molecular beam epitaxy (PAMBE). Growth and characterization of N-polar HEMT structures with ultra-thin channel (3 nm) using InAlN on on-axis GaN and SiC substrates by PAMBE. A thorough investigation and examination into the scaling behavior of the channel and its impact on charge density and electron mobility. Fabrication and characterization of ultra-thin-channel N-polar HEMTs with and without gate recess
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jul 20, 2020
- Source ID
- N000142012658
Entities
People
- Elaheh Ahmadi
Organizations
- Board of Regents of the University of Michigan
- Office of Naval Research
- United States Navy