High Performance Buffers for RF GaN Electronics
Lead Research Organisation:
University of Bristol
Department Name: Physics
Abstract
AlGaN/GaN high electron mobility transistors (HEMTs) are a key enabling technology for future power conditioning applications in the low carbon economy, and for high efficiency military and civilian microwave systems. GaN-on-Si is highly attractive as a low cost, medium performance technology platform which has been proved to be usable even up to the W-band. The main down-sides of Si are the low bandgap and hence resistive lossy substrate especially at modest elevated temperatures, the vulnerability of the Si to unintentional doping with gallium during epitaxy causing RF losses, and the somewhat restricted power handling resulting from the relatively low thermal conductivity of the Si compared to the 4" SiC growth substrates currently used. However the cost benefits are dramatic allowing 6" or even 8" high volume wafer processing. 6" GaN-on-Si epitaxy is already available driven by the emerging GaN-on-Si power switch market, however it is optimised for high voltage, switched-mode operation. Improved RF power amplifier (PA) efficiency using GaN-on-Si, which is the focus of this proposal, would reduce the transistor temperature rise, reduce the substrate losses and deliver a low-cost high-performance technology as it would reduce the transistor temperature rise and reduce the substrate losses. The advance that is required is an optimised RF specific GaN-on-Si transistor architecture, which requires detailed understanding of electronic traps introduced into the GaN buffer of these devices by iron, carbon and carbon/iron co-doping, which is presently lacking. The key aim of this proposal is to control and model the device capacitances and conductances using novel epitaxial design of the GaN buffer, as this is key to delivering improved efficiency, gain and linearity in RF amplifiers.
Planned Impact
GaN-on-Si for RF is a game-changer, with low cost high RF power capability likely to be available shortly, and this is only just beginning to be recognised by industry. Aiding the implementation of GaN-on-Si for RF, which is the aim of this proposal, would therefore result in major economic benefit for the UK from this emerging GaN HEMT technology either directly through epitaxial wafer supply, or indirectly through its application in the microwave systems industries. The availability of high performance GaN is of direct benefit to M/A-COM UK who have device manufacture in the US but system design and manufacture in the UK. UK aeronautics, space & defence companies (Selex UK, Astrium, Airbus, MBDA, BAESYSTEMS etc) will similarly benefit from the dramatic fall in RF component costs that will follow. These companies need to understand and de-risk any new technology before it can be implemented cost-effectively. It is expected that GaN-on-Si technology will become the dominant solid-state PA technology in the future, but this has not yet happened essentially due to component cost, investment hurdles, and a lack of experience and confidence on the part of systems companies. GaN-on-Si for power switching electronics will sweep aside those investment hurdles and it has been estimated that at maturity GaN-on-Si for RF will cut the cost to a third that of current high-volume GaAs RF technology. This project uses direct links between the Universities of Bristol and Cardiff to two world leading enterprises with highly advanced GaN activities, giving a tangible benefit to those companies. IQE, based in Cardiff, is the world's largest specialist epitaxy supplier with more than 50% of the market, and has GaN-on-Si epitaxial development underway in both Cardiff and the USA at 100mm, 150mm and 200mm scale. M/A-COM is a leading supplier of high performance analogue RF, microwave, millimeterwave and photonic semiconductor products that enable next-generation internet and modern battlefield applications. They have established GaN-on-SiC and Si processes for RF, both in-house and outsourced. IQE and M/A-COM have put in place a strategic supply agreement for GaN epitaxial products.
Organisations
Publications
Singh M
(2018)
"Kink" in AlGaN/GaN-HEMTs: Floating Buffer Model
in IEEE Transactions on Electron Devices
Uren M
(2017)
"Leaky Dielectric" Model for the Suppression of Dynamic $R_{\mathrm{ON}}$ in Carbon-Doped AlGaN/GaN HEMTs
in IEEE Transactions on Electron Devices
Chandrasekar H
(2018)
Buffer-Induced Current Collapse in GaN HEMTs on Highly Resistive Si Substrates
in IEEE Electron Device Letters
Mishra A
(2020)
Characterization of trap states in buried nitrogen-implanted ß -Ga2O3
in Applied Physics Letters
Hirshy H
(2018)
Evaluation of Pulsed I - V Analysis as Validation Tool of Nonlinear RF Models of GaN-Based HFETs
in IEEE Transactions on Electron Devices
Kabouche R
(2019)
High Efficiency AlN/GaN HEMTs for Q-Band Applications with an Improved Thermal Dissipation
in International Journal of High Speed Electronics and Systems
Uren M
(2021)
Impact of carbon in the buffer on power switching GaN-on-Si and RF GaN-on-SiC HEMTs
in Japanese Journal of Applied Physics
Singh M
(2019)
Lateral charge spreading and device-to-device coupling in C-doped AlGaN/GaN-on-Si wafers
in Microelectronics Reliability
Chatterjee I
(2017)
Lateral Charge Transport in the Carbon-Doped Buffer in AlGaN/GaN-on-Si HEMTs
in IEEE Transactions on Electron Devices
Wach F
(2020)
Low Field Vertical Charge Transport in the Channel and Buffer Layers of GaN-on-Si High Electron Mobility Transistors
in IEEE Electron Device Letters
Singh M.
(2019)
Misinterpretation of drain transient spectroscopy in GaN HEMTs: Explanation using a floating buffer model
in CS MANTECH 2019 - 2019 International Conference on Compound Semiconductor Manufacturing Technology, Digest of Papers
Butler P
(2018)
Neutron Irradiation Impact on AlGaN/GaN HEMT Switching Transients
in IEEE Transactions on Nuclear Science
Butler P
(2018)
Ohmic Contact-Free Mobility Measurement in Ultra-Wide Bandgap AlGaN/AlGaN Devices
in IEEE Electron Device Letters
Singh M
(2018)
Pulsed Large Signal RF Performance of Field-Plated Ga 2 O 3 MOSFETs
in IEEE Electron Device Letters
Chandrasekar H
(2019)
Quantifying Temperature-dependent Substrate Loss in GaN-on-Si RF Technology
Chandrasekar H
(2019)
Quantifying Temperature-Dependent Substrate Loss in GaN-on-Si RF Technology
in IEEE Transactions on Electron Devices
Pomeroy J
(2019)
Raman Thermography of Peak Channel Temperature in $\beta$ -Ga 2 O 3 MOSFETs
in IEEE Electron Device Letters
Rackauskas B
(2019)
Reliability and lifetime estimations of GaN-on-GaN vertical pn diodes
in Microelectronics Reliability
Yang F
(2022)
Study of Drain Injected Breakdown Mechanisms in AlGaN/GaN-on-SiC HEMTs
in IEEE Transactions on Electron Devices
Yang F
(2020)
The Impact of Hot Electrons and Self-Heating During Hard-Switching in AlGaN/GaN HEMTs
in IEEE Transactions on Electron Devices
Wohlfahrt M
(2021)
UV-induced change in channel conductivity in AlGaN/GaN high electron mobility transistors to measure doping
in Applied Physics Letters
Wohlfahrt M
(2021)
Vertical field inhomogeneity associated with threading dislocations in GaN high electron mobility transistor epitaxial stacks
in Applied Physics Letters
| Description | New models for buffers in GaN electronics were developed |
| Exploitation Route | IQEis in process implementing buffers developed |
| Sectors | Aerospace Defence and Marine Electronics |
| Description | Improved power and RF electronic devices resulted from this work. IQE is in process implementing those in their production line in South Wales. |
| First Year Of Impact | 2019 |
| Sector | Aerospace, Defence and Marine,Electronics |
| Impact Types | Economic |
| Title | Raman thermography of peak channel temperature in ß-Ga2O3 MOSFETs |
| Description | Research group data, Center for Device Thermography and Reliability, microwave and power semiconductor electronic devices and materials James Pomeroy to be deputy steward |
| Type Of Material | Database/Collection of data |
| Year Produced | 2018 |
| Provided To Others? | Yes |