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A study of current transport across metal to clean silicon interfaces

Heatley, Robert (1980) A study of current transport across metal to clean silicon interfaces. Doctor of Philosophy (PhD) thesis, University of Kent. (doi:10.22024/UniKent/01.02.94408) (KAR id:94408)


A detailed study has been made into the current transport across metal to clean silicon interfaces. The metals considered for the experimental work were gold, chromium, silver and aluminium. The experimental procedure involved the deposition of the metal film onto the clean silicon surface under ultra-high vacuum ( U .H . V .) conditions. Two techniques were used for the attainment of a clean silicon surface. Epitaxial layers were deposited by sublimation under U . H . V . conditions onto heat cleaned substrates and also a straight forward heat cleaning treatment was used in order to produce the required surface. In each case the U . H . V . heat cleaning treatment involved resistively heating the substrate to a temperature of 1200°C for 5 minutes. This technique was essential to the epitaxial layer deposition in order to remove the oxide layer and other contamination and to eliminate any interfacial layer when just considering the heat cleaned surfaces. Cleaving under U . H . V . conditions was considered doubtful due to the residual strain which might distort the surface region. Due to the fact that intimate metal-silicon contacts are being considered the conventional surface state analysis is definitely not the most applicable in this case. A theoretical model has been developed based on the effects of metal quantum states decaying into the band-gap of the semiconductor. These states are known as quantum tails. A comprehensive data analysis technique has been used which indicates good agreement between the experimental barrier heights, for both interface formation techniques, and the potential profile in the depletion layer predicted by the model. The variation of barrier height with the various metals used can be explained in terms of the density and distribution of the metal induced surface states in the semiconductor band-gap. Finally the departures of the current- voltage characteristics from the usual approximation of thermionic emission can be explained in terms of the variation of the effective barrier height under differing bias conditions. This effect can be seen to be due to the variations of the charge in the quantum tails under varying bias conditions. To the author's knowledge this is the first time that data has been reported for metal contacts onto epitaxial silicon layers. Also good correlation has been achieved with the results from the two surface preparation methods. Further work of interest has been considered with a view to refining the experimental procedure and hopefully producing a more comprehensive understanding of the behaviour at the interface.

Item Type: Thesis (Doctor of Philosophy (PhD))
Thesis advisor: Bennett, R.J.
DOI/Identification number: 10.22024/UniKent/01.02.94408
Additional information: This thesis has been digitised by EThOS, the British Library digitisation service, for purposes of preservation and dissemination. It was uploaded to KAR on 25 April 2022 in order to hold its content and record within University of Kent systems. It is available Open Access using a Creative Commons Attribution, Non-commercial, No Derivatives ( licence so that the thesis and its author, can benefit from opportunities for increased readership and citation. This was done in line with University of Kent policies ( If you feel that your rights are compromised by open access to this thesis, or if you would like more information about its availability, please contact us at and we will seriously consider your claim under the terms of our Take-Down Policy (
Uncontrolled keywords: Solid-state physics, current transport
Subjects: Q Science > QC Physics
T Technology > TK Electrical engineering. Electronics. Nuclear engineering
Divisions: Divisions > Division of Computing, Engineering and Mathematical Sciences > School of Engineering and Digital Arts
SWORD Depositor: SWORD Copy
Depositing User: SWORD Copy
Date Deposited: 07 Feb 2023 15:51 UTC
Last Modified: 07 Feb 2023 15:51 UTC
Resource URI: (The current URI for this page, for reference purposes)

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