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Density Functional Theory (DFT) study of GaN(0001) surface in ammonia rich conditions - influence of doping type

Pawel Kempisty 1Pawel Strak 1Stanisław Krukowski 1,2

1. Polish Academy of Sciences, Institute of High Pressure Physics (UNIPRESS), Sokolowska 29/37, Warszawa 01-142, Poland
2. Warsaw University, Interdisciplinary Centre for Materials Modelling (ICMM), Pawinskiego 5a, Warszawa 02-106, Poland


Density Functional Theory (DFT) calculations were used to study the GaN(0001) surface  covered with H adatoms, NH3 admolecules and NH2 radicals. This corresponds to physical conditions during GaN growth by hydride vapor phase epitaxy (HVPE), metalorganic vapor phase epitaxy (MOVPE) or ammonothermal methods. In comparison to the earlier work of other authors [1], the reported calculations were based on larger size representation of the surface i.e. the slabs of lateral size 4x4 were routinely used. In addition, the effect of doping type on the stability of the layer covering the surface was examined. The results show that the different doping in the bulk can lead to slightly different surface coverage. For some specific surface coverage the pinning of the Fermi level on surface states and the band bending disappears. In this case the doping of the semiconductor bulk (p-type, semiinsulating or n-type) and the related Fermi level is extremely important in the context of the stability of the surface and the possible adsorption/desorption processes. This phenomenon is observed in a narrow coverage range which entails use a large size of the simulated domain, allowing to control small changes in the surface coverage.

[1] C. G. Van de Walle and J. Neugebauer, Phys. Rev. Lett. 88, 066103 (2002)


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Presentation: Poster at 15th Summer School on Crystal Growth - ISSCG-15, by Pawel Kempisty
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Submitted: 2013-07-03 16:25
Revised:   2013-07-03 16:27