Keywords: semiconductors, heterostructures, low noise electronics, high speed electronics, resonant tunnelling
Start Date: 1 April 95 / Duration: 36 months
[ participants / contact]
The aim of the project is to improve understanding of the different noise sources in compound semiconductors and high electron mobility transistor (HEMT) structures which is most important for low-noise high-speed electronics. Electron drift velocity, AC response, diffusivity and spectral density of fluctuations will be studied, independent of the band structure, the doping level, interelectrodal distance and ambient temperature. The main emphasis will be put on the physical, geometrical, and process-dependent parameters which influence the noise behaviour of compound semiconductors and heterostructures both at low frequencies and microwave frequencies in particular when the electric field strength increases.
The noise contribution in HEMT-based structures due to purely physical processes in the channel will be separated from that of the design. Contributions originating from device matching and the thermal regime will be estimated. In addition, noise in tunnelling junctions will be investigated. The analysis of excess noise in heterostructure barriers will give new insight into noise phenomena of future resonant-tunnelling devices.
Noise measurements have been performed in lateral and vertical homoepitaxial and heteroepitaxial layers (InP/InGaAs, GaAs/AlGaAs). Low frequency noise measurements and correlation with new models (analytic as well as Monte Carlo) were used to characterise the influence of trap levels, substrate and surface passivation used for the fabrication of pseudomorphic InP/InGaAs HEMTs of different compositions.
A new technique enables measurement of excess noise at high electric fields. Hot electron noise in homoepitaxial material, as well as in quantum wells, has been characterised by this means.
Results obtained so far have been presented at workshops and international conferences and published in international journals. The international workshop on Compound Semiconductor Devices and Integrated Circuits that took place in May 1996 was organised by the Lithuanian partners in Vilnius. An this workshop, eight of the 68 contributions have been given by the partners of this cooperation. Annual workshops are also planned that will be open only to a limited number of external participants.
Technische Hochschule Darmstadt
D-64283 Darmstadt, D
Technische Hochschule Darmstadt, D
Rheinisch-Westfälische Technische Hochschule Aachen, D
Semiconductor Physics Institute, LT
Institute of Electronic Materials Technology ( ITME ), PL
Research Institute for Technical Physics, HU
A.F. Ioffe Physical Technical Institute, RU
Prof. Dr.Eng. H.L. Hartnagel
Tel: +49 6151 16 21 62
Fax: +49 6151 16 43 67
NOISE - CP94-1180, May 1997
please address enquiries to the ESPRIT Information Desk
html version of synopsis by Nick Cook