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Interface characteristics of n-n and p-n Ge/SiC heterojunction diodes formed by molecular beam epitaxy deposition

Interface characteristics of n-n and p-n Ge/SiC heterojunction diodes formed by molecular beam epitaxy deposition
Interface characteristics of n-n and p-n Ge/SiC heterojunction diodes formed by molecular beam epitaxy deposition
In this article, we report on the physical and electrical nature of Ge/SiC heterojunction layers that have been formed by molecular beam epitaxy (MBE) deposition. Using x-ray diffraction, atomic force microscopy, and helium ion microscopy, we perform a thorough analysis of how MBE growth conditions affect the Ge layers. We observe the layers developing from independent islands at thicknesses of 100 nm to flat surfaces at 300 nm. The crystallinity and surface quality of the layer is shown to be affected by the deposition parameters and, using a high temperature deposition and a light dopant species, the layers produced have large polycrystals and hence a low resistance. The p-type and n-type layers, 300 nm thick are formed into Ge/SiC heterojunction mesa diodes and these are characterized electrically. The polycrystalline diodes display near ideal diode characteristics (n<1.05), low on resistance and good reverse characteristics. Current-voltage (I-V) measurements at varying temperature prove that all the layers have two-dimensional fluctuations in the Schottky barrier height (SBH) due to inhomogeneities at the heterojunction interface. Capacitance-voltage analysis and the SBH size extracted from I-V analysis suggest strongly that interface states are present at the surface causing Fermi-level pinning throughout the bands. A simple model is used to quantify the concentration of interface states at the surface.
0021-8979
1-8
Gammon, P. M.
4265bdbe-fcc4-4b87-b822-c487c0ac0405
Perez-Tomas, A.
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Jennings, M. R.
b7265ea7-9db0-48c8-bb9a-abbdf666fdb3
Shah, V. A.
71808315-e1ac-4b0e-b2ac-7aae23bf0b9a
Boden, S. A.
83976b65-e90f-42d1-9a01-fe9cfc571bf8
Davis, M. C.
6f35fccb-258f-48d9-b7e5-116d31e1ec8f
Burrows, S. E.
b167c5bd-82e3-4a22-b4fa-a379e152ece8
Wilson, N. R.
44f3a163-dc89-4e28-9dbe-80ff364bb471
Roberts, G. J.
4345c894-c43b-44ac-a938-e7ac021bf033
Covington, J. A.
73618cb5-38fc-48ee-abaf-3fc73d1a84ca
Mawby, P. A.
f59bac97-66dd-4474-9a7c-2237a71b91ce
Gammon, P. M.
4265bdbe-fcc4-4b87-b822-c487c0ac0405
Perez-Tomas, A.
9f38cec1-65ed-4e7f-aa3d-2c93d1aeeae7
Jennings, M. R.
b7265ea7-9db0-48c8-bb9a-abbdf666fdb3
Shah, V. A.
71808315-e1ac-4b0e-b2ac-7aae23bf0b9a
Boden, S. A.
83976b65-e90f-42d1-9a01-fe9cfc571bf8
Davis, M. C.
6f35fccb-258f-48d9-b7e5-116d31e1ec8f
Burrows, S. E.
b167c5bd-82e3-4a22-b4fa-a379e152ece8
Wilson, N. R.
44f3a163-dc89-4e28-9dbe-80ff364bb471
Roberts, G. J.
4345c894-c43b-44ac-a938-e7ac021bf033
Covington, J. A.
73618cb5-38fc-48ee-abaf-3fc73d1a84ca
Mawby, P. A.
f59bac97-66dd-4474-9a7c-2237a71b91ce

Gammon, P. M., Perez-Tomas, A., Jennings, M. R., Shah, V. A., Boden, S. A., Davis, M. C., Burrows, S. E., Wilson, N. R., Roberts, G. J., Covington, J. A. and Mawby, P. A. (2010) Interface characteristics of n-n and p-n Ge/SiC heterojunction diodes formed by molecular beam epitaxy deposition. Journal of Applied Physics, 107 (124512), 1-8.

Record type: Article

Abstract

In this article, we report on the physical and electrical nature of Ge/SiC heterojunction layers that have been formed by molecular beam epitaxy (MBE) deposition. Using x-ray diffraction, atomic force microscopy, and helium ion microscopy, we perform a thorough analysis of how MBE growth conditions affect the Ge layers. We observe the layers developing from independent islands at thicknesses of 100 nm to flat surfaces at 300 nm. The crystallinity and surface quality of the layer is shown to be affected by the deposition parameters and, using a high temperature deposition and a light dopant species, the layers produced have large polycrystals and hence a low resistance. The p-type and n-type layers, 300 nm thick are formed into Ge/SiC heterojunction mesa diodes and these are characterized electrically. The polycrystalline diodes display near ideal diode characteristics (n<1.05), low on resistance and good reverse characteristics. Current-voltage (I-V) measurements at varying temperature prove that all the layers have two-dimensional fluctuations in the Schottky barrier height (SBH) due to inhomogeneities at the heterojunction interface. Capacitance-voltage analysis and the SBH size extracted from I-V analysis suggest strongly that interface states are present at the surface causing Fermi-level pinning throughout the bands. A simple model is used to quantify the concentration of interface states at the surface.

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More information

Published date: 25 June 2010
Organisations: Nanoelectronics and Nanotechnology

Identifiers

Local EPrints ID: 272657
URI: https://eprints.soton.ac.uk/id/eprint/272657
ISSN: 0021-8979
PURE UUID: 72710063-548c-4a04-80bd-898cf82808a4
ORCID for S. A. Boden: ORCID iD orcid.org/0000-0002-4232-1828

Catalogue record

Date deposited: 11 Aug 2011 13:37
Last modified: 06 Jun 2018 12:43

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