The self-assembled GaN hexagonal micropyramid and microdisk were grown on LiAlO2 by plasma-assisted molecular-beam epitaxy. It was found that the (0001¯) disk was established with the capture of N atoms by most-outside Ga atoms as the (1×1) surface was constructing, while the pyramid was obtained due to the missing of most-outside N atoms. The intensity of cathode luminescence excited from the microdisk was one order of amplitude greater than that from M-plane GaN.

Spin-splitting energies of wurtzite AlN and InN are calculated using the linear combination of atomic orbital method, and the data are analyzed utilizing the two-band k • p model. It is found that in the k • p scheme, a spin-degenerate surface exists in the wurtzite Brillouin zone. Consequently, the D'yakonov-Perel' spin relaxation mechanism can be effectively suppressed for all spin components in the ͓001͔-grown wurtzite quantum wells ͑QWs͒ at a resonant condition through application of appropriate strain or a suitable gate bias. Therefore, wurtzite QWs ͑e.g., InGaN/AlGaN and GaN/ AlGaN͒ are potential structures for spintronic devices such as the resonant spin lifetime transistor.

The edge and threading dislocations of M-plane GaN epilayers grown on γ-LiAlO2 have been studied by high-resolution transmission electron microscope. We found that edge dislocations were grown in [11¯00] direction while threading dislocations were generated along a1 or −a2 axes. We also observed a single stacking fault in the M-plane GaN epilayer.

We have grown M-plane GaN films with self-assembled C-plane GaN nanopillars on a -LiAlO 2 substrate by plasma-assisted molecular-beam epitaxy. The diameters of the basal plane of the nanopillars are about 200 to 900 nm and the height is up to 600 nm. The formation of self-assembled c-plane GaN nanopillars is through nucleation on hexagonal anionic bases of -LiAlO 2 . Dislocation defects were observed and analyzed by transmission electron microscopy. From the experimental results, we developed a mechanism underlying the simultaneous growth of three-dimensional c-plane nanopillars and twodimensional M-plane films on a -LiAlO 2 substrate.

No abstract