Metal Contacts on a-GaN
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Internet Journal of Nitride Semiconductor Research:
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Metal Contacts on a-GaN T. U. Kampen and W. Mönch MRS Internet Journal of Nitride Semiconductor Research / Volume 1 / January 1996 DOI: 10.1557/S1092578300002131, Published online: 13 June 2014
Link to this article: http://journals.cambridge.org/abstract_S1092578300002131 How to cite this article: T. U. Kampen and W. Mönch (1996). Metal Contacts on a-GaN . MRS Internet Journal of Nitride Semiconductor Research, 1, pp e41 doi:10.1557/S1092578300002131 Request Permissions : Click here
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M R S
Internet Journal o f
Nitride S emiconductor Research
Volume 1, Article 41
Metal Contacts on a-GaN T. U. Kampen, W. Mönch Laboratorium fuer Festkoerperphysik, Gerhard-Mercator-Universitaet Duisburg This article was received on June 2, 1996 and accepted on December 16, 1996.
Abstract The Schottky barrier heights of silver and lead contacts on n -type GaN (0001) epilayers were determined from current-voltage characteristics. The zero-bias barrier heights and the ideality factors were found to be linearly correlated. Similar observations were previously reported for metal contacts on Si (111) and GaAs (110) surfaces. The barrier heights of ideal Schottky contacts are characterized by image force lowering of the barrier only. This gives an ideality factor of 1.01. From our data we obtain barrier heights of 0.82 eV and 0.73eV for ideal Ag and Pb contacts on GaN, respectively. The metal-induced gap states (MIGS) model predicts the barrier heights of ideal Schottky contacts on a given semiconductor to be linearly correlated with the electronegativities of the metals. The two important parameters of this MIGS-and-electronegativity model are the charge neutrality level (CNL) of the MIGS and a slope parameter. The CNL may be calculated from the dielectric band gap and using the empirical tight-binding method. The slope parameters are given by the optical dielectric constant of the respective semiconductor. The predictions of the MIGS model for metal/GaN contacts are confirmed by the results presented here and by barrier heights previously reported by others for Au, Ti, Pt, and Pd contacts on GaN.
1. Introduction Most metal-semiconductor contacts are rectifying. The electronic transport across such Schottky contacts is characterized by their barrier heights. The barrier height is the energy distance between the Fermi level W F and the respective majority carrier band edge at the interface (respectively, the valence-band maximum W vi for p- and the conduction-band minimum W ci for n-type semiconductors). The famous Schottky-Mott rule [1] [2] predicts the barrier height to be equal to the difference between the electron affinity of the semiconductor and the work function of the metal. Schweikert (see [3]) was the first to test this rule. He found the barrier heights of metal-Se contact
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