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Cryogenic 3D Nanoelectronics

Periodic Reporting for period 1 - SEQUENCE (Cryogenic 3D Nanoelectronics)

Reporting period: 2020-01-01 to 2021-06-30

The SEQUENCE project uses unconventional approaches to develop electronics for low temperature operation. The goal is to enable quantum computers to scale up to be able to tackle a variety of important technological and scientific problems as well as improve satellite and terrestrial communication systems.
Electronics cooled to very low temperatures will have a strong impact on our society through applications spanning space communication, high performance computing, and quantum enhanced computing. Quantum computers, for instance, have the potential to radically advance our computational capability and are predicted to strongly influence fields such as medicine, chemistry, science and finance by solving computational problems that cannot readily be solved by classical computers. The project develops a variety of high frequency circuits that operate at low power levels and also utilize the low operating temperature to achieve high performance.
The overall objectives are

- 3D Electronics: To integrate devices and circuits using 3D stacking to significantly reduce the number of physical components required for low temperature systems.
- Cryogenic Electronics: To develop a new generation low-power, low-temperature electronics for scalable quantum computers.
- Cryogenic Transistors: To develop and validate transistor and circuit models for low temperatures.
- Nanoelectronics Devices: To develop novel nanoelectronic devices operating at low temperatures.
- Develop Synergies: To use the low temperature and 3D integration technology for space and terrestrial communication applications.
During the first part of the project a large effort has been put on the development of fabrication techniques and low temperature characterisation since it is important to understand device behaviour at low temperature to be able to design and fabricate circuits. The main results obtained thus far are

1. A very low contact resistance between metal contacts and InGaAs using acid and ion-gun pretreatment.
2. III-V and Si transistors have been measured down to -273°C and modelling used to describe the devices have been developed.
3. Transistors have been measured using short voltage pulses which gave a significant improvement in performance.
4. Conventional transistors (MOSFETs) have been integrated with novel tunneltransistors utilizing quantum mechanical effects to lower the power consumption.
5. Amplifier circuits with a record high performance at low temperature has been demonstrated.
The low noise amplifier (LNA) circuit developed is the highest performing integrated circuit LNA for low temperatures fabricated in a foundry process. The contact resistance on InGaAs is are one of the lowest reported. The transistor modeling describing the low temperature behaviour is also at the forefront of the field. Another notable progress beyond state of the art is the cointegration of conventional and tunneltransistors since this achievement opens up many new possibilities within this field.

During the second part of the project, we expect to achieve more results on the circuit level and especially on 3D co-integration of different technologies. Such results will have a large impact in the fields of quantum computers, space communication, high-performance computing and wideband communication. These technological areas are of high importance and are therefore expected to have large economic and societal impact.