Evaluations of the microstructures at the interface between the semipolar (103) AlN epilayer and the m-plane (100) sapphire substrate

Abstract

We investigate the microstructures at the interface between the semipolar (103) AlN epilayer and the m-plane (100) sapphire substrate using electron microscopy techniques. The formation of inverted triangular voids in the sapphire substrate side with {110}_sapphire sidewalls is observed. Inclined arrowhead features, pointing in the c-axis [0001]_AlN direction, are observed in the AlN epilayer side. Lattice-polarity verification confirms that the arrowhead feature relates to the lattice-polarity inversion. Meanwhile, threading dislocations (TDs) propagating to the surface and basal-plane stacking faults (BSFs) lying on the (0001) plane are observed. The lattice-polarity of the final semipolar (103) AlN epilayer is determined to be Al-polar. In addition, an accumulation of Si at the inversion domain boundary (IDB) is found using energy dispersive X-ray spectroscopy (EDS) measurements. The investigation results provide important hints towards understanding and controlling the epilayer growth.