Temperature dependence of the thermal expansion of GaN

The thermal expansion of hexagonal GaN bulk crystals was studied in an extended temperature range from 120.3em0exto0.3em0ex10250.3em0exK. 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)0.3em0exK and (898±24)0.3em0exK and Einstein temperatures of (636±13)0.3em0exK and (662±18)0.3em0exK were derived along the a and c axes, respectively, and compared to available literature values.