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The growth mechanism and the crystallinity of hydrothermally synthesized nonpolar a-plane ZnO (a-ZnO) on a-plane GaN template were investigated by using epitaxial lateral overgrowth (ELO) patterns parallel or perpendicular to the c-axis direction. Due to the anisotropic growth rates along the specific crystallographic directions, lateral overgrowth of a-ZnO was observed only for ZnO grown on the ELO stripe patterns perpendicular to the c-axis direction. In X-ray diffraction analysis, a-ZnO grown on the c-axis parallel patterns had smaller FWHM values of the X-ray rocking curves along the X-ray in-beam orientations in the c-and the m-axis directions. © The Author There has been great interest in nitride-based wide bandgap semiconductors for solid state lighting applications. Commercially available light-emitting diodes (LEDs) are mostly based on gallium nitride (GaN) related material system, which is grown along the polar c-axis [0001] of wurtzite crystal structure on c-plane sapphire substrate. In this crystal plane, there exist the spontaneous and piezoelectric polarizations inducing internal electric fields, which result in spatial separation of electron and hole wave functions.1,2 This quantum confined stark effect causes the reduction in radiative recombination efficiency in quantum well structure. [3][4][5] As an alternative approach, extensive efforts have been exerted to eliminate the internal electric field using nonpolar or semipolar GaN crystals. [6][7][8][9] ZnO is a promising light-emitting material due to its wide direct bandgap of 3.37 eV and larger exciton binding energy of 60 meV than that of GaN. Various growth methods for ZnO epitaxial layer have been reported such as metal organic chemical vapor deposition, molecular beam epitaxy, pulsed laser deposition, and hydrothermal synthesis.10-14 Among these deposition techniques, hydrothermal growth is one of the most facile and cost-effective methods due to its atmospheric growth pressure and significantly low process temperature. Recently, we have reported nonpolar a-plane ZnO (a-ZnO) film grown on a-plane GaN (a-GaN) template by hydrothermal method, which can act as a light-emitting active layer of nonpolar n-type ZnO/p-type GaN heterostructure LED.2,15 However, the crystal quality of hydrothermally grown a-ZnO has much room for improvement compared with conventional GaN epitaxial layer. The growth mechanism also needs to be further understood. It is generally accepted that epitaxial lateral overgrowth (ELO) technique can successfully enhance material quality of GaN. Crystal defects such as threading dislocations are significantly reduced on the masking area because these dislocations stemming from window region cannot be extended over masked pattern. Since ZnO has the same wurtzite crystal structure as GaN and the similar growth mechanism of island nucleation is involved on lattice mismatched foreign substrates, the ELO technique can be also applied to hydrothermal growth of ZnO. [16][17][18][19] In this work, we investigated the growth mechanism,...

We investigated the spatial variation of energy band structure in a SrTiO3 (001) bicrystal with the (100) 10° tilt boundary before and after the annealing process at 973 K under a vacuum of ~10-7 Torr and after the subsequent forming process with electrical dielectric breakdown, using electron beam induced current (EBIC) method in the temperature range between 200 and 300K. Although the EBIC contrast at the tilt boundary was weak before and after the annealing, it became visible after the forming process and stronger as the observation temperature decreased to less than 260 K. It was found that the EBIC direction at the tilt boundary is opposite to that in the matrix, i.e. the single crystalline regions of both sides of the tilt boundary. In the matrix, the EBIC increased after the annealing and decreased again after the forming process. We propose energy band structures of the bicrystalline SrTiO3 after the annealing and after the forming process.