Silicon Resonant Tunnelling Diodes and Circuits

Lead Research Organisation: University of Glasgow
Department Name: School of Engineering


Resonant tunnelling diodes (RTDs) are one of the few quantum device technologies which has made production with superior performance compared to rival devices and circuits. All such circuits have been in III-V technology while over 98% of microelectronic sales are silicon devices. Previous work at Cambridge has demonstrated III-V type performance from Si/SiGe RTDs. This proposal is to develop and demonstrate basic circuits using Si/SiGe RTDs combined with strained-Si MOSFETs, a key step required if such technology is to make the leap to production. One application will be investigated as a demonstrator, that of tunnelling static random access memory (TSRAM). The TSRAM has the ability to be integrated with future CMOS microprocessors using strained-Si technology, hence the inclusion in the International Technology Roadmap for Semiconductors (ITRS) of RTD technology. In particular the TSRAM potentially offers 7 orders of magnitude improvement in CMOS SRAM standby power dissipation, now one of the most important parameters in the future scaling of CMOS microprocessors. We also propose to develop existing outreach teaching resources on Moore's law, scaling and post Moore devices to encourage children into science and the U.K. semiconductor industry linked to the proposed research.The work we propose is also aligned with the EPSRC Signposted Grand Challenges in Silicon Technology as set out by the U.K. EPSRC Silicon Futures network (GR/T07879). This particular proposal to some degree straddles all the Technology Grand Challenges but the change of device architecture to RTDs with ~2 nm critical dimensions is most strongly aligned to the G1: Novel Devices and Processes Using Silicon Based Technology. This proposal will develop and validate quantum device models of RTDs (G2.2) and use numerous characterisation techniques at the nm scale (G3). The RTD technology is using SiGe and so we are addressing G4: New Materials Systems for Silicon Based Technologies. As standby power dissipation is also reduced by 7 orders of magnitude compared to SRAM, this is also aligned with the G7 Eco-silicon Grand Challenge and the many potential applications for a successful technology especially with DAC and ADC circuits has strong associations with the G6 Silicon for Life Grand Challenge.


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Mirza M (2012) Nanofabrication of high aspect ratio (~50:1) sub-10 nm silicon nanowires using inductively coupled plasma etching in Journal of Vacuum Science & Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena

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Ternent G (2013) Si/SiGe Tunneling Static Random Access Memories in ECS Transactions

Description Si/SiGe and AlGaAs/GaAs resonant tunneling diodes
(RTDs) were realized using a self-aligned fabrication process with dimensions ranging from 50 µm down to 30 nm. Using these devices, scaling rules are developed and incorporated into a modified SPICE model. The depletion width and the sidewall current are extracted from the model. The results confirm that the parasitic sidewall current is responsible for the reduction in peak-to-valley current ratio (PVCR) in small-diameter RTDs. A new device layout is demonstrated to significantly reduce the sidewall current for optimum nanoscale performance. Improvements in the PVCRs are demonstrated by this approach. The first TSRAM on a silicon platform was also demonstrated.
Exploitation Route Further research is required to take this to a scaled demonstrator before industry will be interested.
Sectors Electronics

Description The outputs were fed into a UK company to help develop medical imaging technology.
Sector Healthcare
Impact Types Economic

Description Roadmap
Geographic Reach Europe 
Policy Influence Type Participation in a national consultation
Description EC Horizon 2020 Future Emerging Technologies
Amount £512,000 (GBP)
Funding ID 613055 
Organisation European Commission 
Sector Public
Country European Union (EU)
Start 02/2014 
End 01/2017
Description EPSRC Supergen
Amount £2,455,231 (GBP)
Funding ID EP/K022156/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Academic/University
Country United Kingdom
Start 11/2013 
End 10/2017
Description Horizon 2020 Future Emerging Technologies
Amount € 3,225,547 (EUR)
Funding ID 766719 
Organisation European Commission 
Sector Public
Country European Union (EU)
Start 11/2017 
End 10/2020
Description Quantum Technology Fellowships
Amount £1,512,465 (GBP)
Funding ID EP/N003225/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Academic/University
Country United Kingdom
Start 07/2015 
End 06/2020
Description III-V RTDs 
Organisation University of Manchester
Country United Kingdom 
Sector Academic/University 
PI Contribution The results from this award have been used by Mo Missous at Manchester to apply for a programme grant on THz systems.
Collaborator Contribution The device technology developed in this award enables the new circuit technology for THz systems.
Impact Submission of programme grant to EPSRC
Start Year 2015
Description BBC news 
Form Of Engagement Activity A broadcast e.g. TV/radio/film/podcast (other than news/press)
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact I was interviewed on BBC Scotland news and a 3 minute broadcast of the interview was on BBC1 Scotland on the 15th October 2014. This is available on the BBC news webpages.
Year(s) Of Engagement Activity 2014