Thermal Expansion of GaN Bulk Crystals and Homoepitaxial Layers
M. Leszczyński, H. Teisseyre, T. Suski, I. Grzegory, M. Boćkowski, J. Jun, B. Pałosz, S. Porowski
High Pressure Research Center, Polish Academy of Sciences, Sokołowska 29/37, 01-142 Warsaw, Poland

K. Pakuła, J.M. Baranowski
Institute of Experimental Physics, Warsaw University, Hoża 69, 00-681 Warsaw, Poland

and A. Barski
CEA-Grenoble, Departement de Recherche Fondamentale sur la Matiere Condensée SP2M, 17 Rue des Martyrs, 38054 Grenoble Cedex 9, France
Full Text PDF
Thermal expansion of gallium nitride was measured using high resolution X-ray diffraction. The following samples were examined: (i) single monocrystals grown at pressure of about 15 kbar, (ii) homoepitaxial layers. The main factor influencing both, the lattice parameters and the thermal expansion coefficient, are free electrons related to the nitrogen vacancies. The origin of an increase in the lattice constants by free electrons is discussed in terms of the deformation potential of the conduction-band minimum. An increase of the thermal expansion by free electrons is explained by a decrease of elastic constants.
DOI: 10.12693/APhysPolA.90.887
PACS numbers: 61.72.Ji, 61.72.Vv