High-temperature thermal expansion of ScAlMgO4 for substrate application of GaN and ZnO epitaxial growth

High-temperature powder X-ray diffraction measurements for ScAlMgO4 ( in space group) grown by Czochralski method were carried out from 303 to 1473 K. The obtained temperature-dependent unit cell parameters were expressed as for the a-axis and for the c-axis, where T is temperature in kelvin. The axial thermal expansion coefficients for the a-axis estimated from the unit cell parameters were comparable to those of GaN and ZnO. A c-plane ScAlMgO4 substrate can be easily obtained with using cleavage plane along c-plane, which is parallel to a-axis. Thus, ScAlMgO4 is one of the promising substrates for c-plane epitaxial growth of GaN and ZnO. High temperature X-ray single crystal structural analysis of ScAlMgO4 demonstrated the mechanism of the nonlinear variation of the obtained cell parameters as a function of temperature.