Cross-sectional TEM imaging of β-Ga2O3 thin films formed on c-plane and a-plane sapphire substrates

We investigated in detail the microstructure of (201)-oriented beta-Ga2O3 thin films on sapphire substrates by transmission electron microscopy (TEM) and electron diffraction. Cross-sectional TEM images of the films on (001) c-plane and (110) a-plane sapphire substrates are composed of four types of regions with different atomic arrangements. The consideration based on the crystal orientation of beta-Ga2O3 showed that the type of TEM images corresponds to the projection direction caused by the rotation of the beta-Ga2O3 unit cell round the normal to the (201) plane. Electron diffraction patterns corresponding to each region can also be explained in the same manner. These support the results of X-ray pole figure measurements in our previous report. Finally, the relationship among the TEM images, the electron diffraction patterns and the rotation angle of unit cell for (201)-oriented beta-Ga2O3 was classified. (C) 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim