Work Area: Alternative Advanced Semiconductor Materials, Devices and Process Steps
Keywords superlattice structures
Start Date: 1 July 92 / Duration: 36 months / Status: running
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Abstract SUPERDEV is studying the electronic properties and device exploitation of superlattice structures. The novel properties associated with superlattices have potential for enhancing the performance of existing heterostructure devices, eg heterojunction bipolar transistors, photodetectors and lasers, and for providing new device concepts, such as superlattice oscillators. Topics which are of particular interest to the Group include growth and fabrication of heterostructure devices containing superlattice structures with thin layers, and hot-electron transport and relaxation mechanisms in superlattice structures.
The SUPERDEV working group is interested in trying to understand the mechanisms governing vertical, hot-electron transport, and carrier relaxation in III-V superlattice structures, and the potential application of superlattices to enhance the performance of existing heterostructure devices or to provide new device concepts.
Topics of interest to the group include: epitaxial growth of fine-period structures based on GaAs/AlGaAs and InGaAs/InAlAs/InP with emphasis on uniformity and interface sharpness: fabrication of heterostructures, particularly transistors with base regions of less than 100nm thick buried deep within the structure; developing theoretical descriptions of electronic transport in superlattices and determining the physical mechanisms governing hot-carrier transport and relaxation; incorporating superlattices in the base regions of heterojunction bipolar transistors to reduce base access resistance and transit times; and using superlattices structures as oscillators or for enhancing photodetectors and lasers.
The group holds biennial meetings on a site-rotational basis to discuss their work on superlattices and other issues relevant to the field of superlattice devices. These meetings also include tours of the host's laboratories. Further bilateral or multilateral meetings will be held to discuss more specific topics, eg. on growth, fabrication, theory, etc ., or to enhance collaborations. Members of the group will attend international conferences and also publish their work. The group will participate in workshops involving other ESPRIT nanoelectronics consortia (3042, 3043, 3133, 6312, 6536, 6719, 6849) and, if appropriate, it will assist these consortia in the organisation of up to one international workshop during the life of the group.
During the first year SUPERDEV has held two meetings on a site-rotational basis. The first meeting was held at DRA and the second was held at TUT. At these meetings the partners described the work being carried out in their laboratories and the progress being made. DRA and CNET have made clear demonstrations of miniband transport in GaAs/AlGaAs and GaAs/AlAs superlattice structures, respectively. CNET have also observed Esaki-Tsu NDR in GaInAs/AlInAs superlattices which extends up to 55 GHz. Light-induced microwave oscillations in GaAs/AlAs have also been observed in GaAs/AlAs superlattices up to 90GHz. CNRS has developed a fully self-aligned process for their InGaAs/InP heterojunction bipolar transitors. Transitors have been fabricated and tested using material grown by both CNRS and TUT. NMRC have fabricated novel long wavelength separate confinement heterostructure and graded-index separate confinement heterostructure quantum well lasers. Initial tests on the former gives threshold current densities of 1.9kV/Acm2 and device efficiencies of 0.16mW/mA. As well as supplying material to CNRS, TUT has been investigating InGaAs/InGaAsP/InP quantum well lasers, a high gain GaAs/AlGaAs avalanche photodetector and a unipolar quantum well avalanche photodetector.
Research on superlattices carried out by the group will lead to general advances in the growth and fabrication of fine-period heterostructure devices. This is a very fruitful area of research which will benefit from the exchange of views and information dissemination within the Working Group. The understanding of the underlying physical processes of vertical transport in superlattices will also broaden the base knowledge in low dimensional semiconductor structures. This is seen as a necessary stepping-stone towards the exploitation of superlattice structures for the enhancement of existing devices and for realising novel device concepts. The devices of interest to the group are perceived to have potential for the field of microelectronics and optoelectronics for future IT requirements.
The working group participated in the Nanoelectronics Symposium at the ESPRIT '92 conference where it presented a poster describing the aims of the group, the research activities of the partners and the facilities at each of the laboratories of the parnters. Members of the group have attended various national and international conferences and meetings where they have presented results of their work. Further information dissemination has been by publications. The principal mode of dissemination of information will continue in the future to be through attendance at national and international conferences, publication of results in journals, and by participating in joint consortia workshops involving other ESPRIT projects and working groups.
Defence Research Agency - UK
St Andrews Road
UK - Great Malvern WR14 3PS
CNET - F
CNRS-L2M - F
National Microelectronics Research Centre - IRL
Tampere University of Technology - SF
Dr. A.W. Higgs
tel +44/684 894965
fax +44/684 896150
SUPERDEV - 7227, August 1994
please address enquiries to the ESPRIT Information Desk
html version of synopsis by Nick Cook