Nature of the highly conducting interfacial layer in GaN films

Hsu, J. W. P.; Hsu, J.W.P.; Lang, D. V.; Lang, D.V.; Richter, S.; Kleiman, R. N.; Kleiman, R.N.; Sergent, A. M.; Sergent, A.M.; Molnar, R. J.; Molnar, R.J.
October 2000
Applied Physics Letters;10/30/2000, Vol. 77 Issue 18
Academic Journal
Using several scanning probe techniques to investigate local electronic properties, we show that the GaN/sapphire interfacial region contains >= ten times higher electron density but with the Fermi level being 50-100 meV deeper in the band gap compared to the less-conducting bulk film. This anomalous behavior cannot be explained by transport in the intrinsic conduction band of GaN. Rather, it points to the existence of a partially filled donor impurity band. We relate the presence of this impurity band conduction to excess oxygen in the region and the defective microstructure at the GaN/sapphire interface. © 2000 American Institute of Physics.


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