Temperature dependence of the thermal expansion of GaN

The thermal expansion of hexagonal GaN bulk crystals was studied in an extended temperature range from 12 to 1025 K. The lattice parameters a and c were measured by high-resolution x-ray diffraction. The temperature dependence of the derived thermal expansion coefficients along the a and c directions could be well described over the entire temperature range within both the Debye model and the Einstein model. Debye temperatures of (868 +/- 20) K and (898 +/- 24) K and Einstein temperatures of (636 +/- 13) K and (662 +/- 18) K were derived along the a and c axes, respectively, and compared to available literature values.