Epitaxial Layers Versus Bulk Single Crystals of GaN. Temperature Studies of Lattice Parameters and Energy Gap
H. Teisseyre, P. Perlin, M. Leszczyński, T. Suski, L. Dmowski, I. Grzegory, S. Porowski, J. Jun
High Pressure Research Center "Unipress", Polish Academy of Sciences, Sokołowska 29/37, 01-142 Warszawa, Poland

and T.D. Moustakas
Boston University, Molecular Beam Epitaxy Laboratory, Department of Electrical, Computer and System Engineering, Boston MA 02215, USA
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Gallium nitride epitaxial layer grown by molecular beam epitaxy and bulk crystal grown at high pressure were examined by using X-ray diffrac­tion methods, and by optical absorption at a wide temperature range. The free electron concentration was 6 × 1017 cm-3 for the layer and about 5 × 1019 cm-3 for the bulk crystal. The experiments revealed a different po­sition of the absorption edge and its temperature dependence for these two kinds of samples. The structural examinations proved a significantly higher crystallographic quality of the bulk sample. However, the lattice constants of the samples were nearly the same. This indicated that a rather different electron concentration was responsible for the different optical properties via Burstein-Moss effect.
DOI: 10.12693/APhysPolA.87.403
PACS numbers: 65.70.+y, 78.50.Ge, 78.66.Fd