Novel AlAs-InGaAs-AlAs Resonant Tunnelling Diodes for THz

Lead Research Organisation: University of Manchester
Department Name: Electrical and Electronic Engineering

Abstract

The Double-Barrier Quantum Well
(DBQW) RTD is considered as the most promising candidate for high-speed functional
devices and THz oscillators at room temperature. For THz oscillators, the highest
frequency of electronic single devices at room temperature reported recently (2016)
is 1.9THz holding much promise for the realisation of compact and efficient electronic
THz oscillators
The DBQW-RTD in its simplest form, consists of a few monolayers undoped quantum
well sandwiched between two undoped layer of barriers of thickness 3 monolayers.
The emitter and collector contact regions are heavily doped. One of the key
technologies for this achievement is the precise control of epitaxial growth of ultrathin
semiconductor heterostructures. The structural design of oscillators and
microfabrication technology are also crucial. To achieve oscillations in the terahertz
regime, this programme will examine a novel RTD structure designs with ultra thin
AlAs tensile barriers and highly compressive InGaAs quantum wells, which effectively
reduces both the operating bias voltage and electron transit time in the collector
depletion region. InGaAs/AlAs RTD oscillator with 0.9-nm-thick barriers will be
studied for fundamental oscillations at frequencies > 1 THz at room temperature. This
programme will examine the integration of RTDs with RF circuits to form complete
narrow band emitters in the THz region for use as high power emitters in CW THz
imaging systems.

Publications

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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/N509565/1 01/10/2016 30/09/2021
1917913 Studentship EP/N509565/1 14/07/2017 31/03/2021 Andrew Hadfield
 
Description InGaAs based asymmetric spacer layer tunnel diodes (ASPAT) have been grown on metamorphic gallium aresenide (GaAs) substrates for the first time. These diodes can operate at zero bias as part of mm-Wave and microwave detectors.

Metamorphic substrates offer advantages over traditional indium phosphide substrates as they are cheaper and less brittle, allowing for easier and cheaper fabrication.

Physical models of ASPAT and resonant tunnelling diodes (RTD) have been created and validated against measured data from real devices. These models have then be used to explore areas of improving the devices.
Exploitation Route By showing that metamorphic substrates can be used to grow ASPAT diodes others could now apply their use to other InGaAS devices such as RTDs. Metamorphic substrates also allow for an additional degree of freedom in the design of semiconductor devices as device materials no longer have to be grown with the same lattice constant as the substrate.
Sectors Electronics