Microstructure of low temperature grown AlN thin films on Si(111)

AlN thin films were grown on HF-etched Si(111) substrates at 400–600 °C by plasma source molecular beam epitaxy. Reflection high energy electron diffraction and transmission electron microscopy studies show that AlN films grown at 400 °C form an initial amorphous region at the interface, followed by c-axis oriented columnar grains with slightly different tilts and twists. AlN films grown at 600 °C showed a significantly reduced amorphous region near the interface promoting an epitaxial growth of AlN with AlN[0001]∥Si[111] and AlN[011̄0]∥Si[112̄] orientations. However, all the films show numerous defects such as stacking faults, dislocations, and grain boundaries.