Work Area: Nanoelectronics
Keywords nanoelectronics, optoelectronics
Start Date: 1 July 92 / Duration: 36 months / Status: running
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Abstract NANOPT focuses on the development of lateral nanometre structures for novel quantum wire lasers and quantum wire modulators by different technologies. In order to assess the potential of the different approaches, the device-relevant physical properties of quantum wire and quantum dot structures will be analysed, mainly by optical spectroscopy and model calculations.
Lateral nanometre structures are highly interesting for future optoelectronic applications, because they should allow the tailoring of device properties by varying device dimensions. As can be shown theoretically, this should lead to improvements in, for example, the band width and the threshold of semiconductor lasers. Up to now, however, no reproducible fabrication technology for these structures exists, so that reliable studies on the properties of quantum wire lasers and modulators are not available. Within the present project, different promising approaches for the fabrication of effectively one- and zero-dimensional structures for optoelectronic devices will be developed. The device-relevant properties will be studied by optical and electrical characterisation techniques. The results of the characterisation will be used for a further optimisation of the technologies.
The consortium will develop GaAs- and InP-based lateral nanometre structures for optoelectronic applications using novel epitaxy techniques and ultrahigh resolution lithography processes. The basic physical properties of the structures will be investigated by sophisticated characterisation techniques including time-resolved spectroscopy, Raman spectroscopy and magneto-optical experiments. Simultaneously, prototypes for future optoelectronic devices (for example, quantum wire lasers) will be developed and evaluated. The results of the different characterisation techniques will then be used to further optimise the nanometre structure design.
During the first year of the project a large number of important results have been achieved by the partners of the consortium. By molecular beam epitaxy on V - groove substrates GaAs/AlAs quantum wires with high quantum efficencies have been obtained. Lateral superlattices with excellent optical properties were realised on 311 oriented GaAs substrates. By high resolution electron beam lithography and wet etching high quantum efficiency wire structures with lateral widths below 10 nm were realised. Overgrown InGaAs/InP quantum wires were developed by low damage dry etching. The samples were characterised in the different partner laboratories, with regard to quantum efficencies, lateral subbands, high excitation effects, stimulated emission, phonon spectra and carrier thermalisation. By the combination of different spectroscopic techniques available in the partner laboratories of the consortium clear lateral;confinement effects have been observed. The work in the theory groups focused on the calculation of optical transitions, phonons, Raman spectra and electron phonon coupling in quantum wires and dots in close relation with the results of the experimental studies.
The results of the present investigations should allow the assessment of the potential of low dimensional structures for optoelectronic applications. The high-resolution device patterning techniques developed here for effectively one- and zero-dimensional structures should also be relevant for improved devices based on 2-D structures. The spectroscopic and theoretical investigations will lead to significant improvements of our understanding of the device-relevant physical properties of low dimensional structures. By close interaction with universities, public research institutions and optoelectronic companies, the results of NANOPT will be made available to all relevant European interest groups.
Results of the research work have been reported in different conferences including the ESPRIT Symposium on Nanoelectronics. International Conferences on related subjects (Hot Carrier Conference, Excitons in Confined Systems) have been organised by partners of the consortium. In October 1993 a workshop on "Optical Properties in Mesoscopic Systems" was held within the Network "Phantoms" at Wuerzburg University.
Universität Wurzburg - D
D - 97074 WÜRZBURG
EPFL - CH
Paul Drude Institut - D
Universität Stuttgart - D
Universidad Autonoma de Madrid - E
Ecole Normale Supérieure - F
INFM-Consorzio Interuniv. Nazionale - I
Universita di Bari - I
University of Oxford - UK
Alcatel Alsthom Recherche - F
Prof. Dr. A. Forchel
tel +49/931 888 5100
fax +49/931 888 5143
NANOPT - 6719, August 1994
please address enquiries to the ESPRIT Information Desk
html version of synopsis by Nick Cook