利用金属有机物化学气相沉积技术生长的a面GaN表面形貌和位错的研究

采用金属有机物化学气相淀积技术在r面蓝宝石衬底上制备了a面GaN薄膜，用熔融的KOH在400 ℃对样品分别腐蚀1.0,1.5和2.0 min.用扫描电镜、原子力显微镜、X射线衍射谱和阴极射线荧光对腐蚀前后的表面形貌进行分析.研究表明，400 ℃下腐蚀1.5 min后出现了长平行四边形的条纹状，这是由于无极化的a面GaN表面极性各向异性，c向与m向上N原子悬挂键密度不同，同时稳定性不同，对OH^-离子的吸附能力不同造成的，其中沿c方向易于腐蚀.同时，a面GaN腐蚀后出现了六角突起.我们认为这与穿透位错有关，而其形貌则与GaN薄膜的位错局部极性有关.关键词：a面GaN')" href="#">a面GaN堆垛层错极性

Morphology and defect of a-GaN grown by metal orgamic chemical vapor deposition

On the substrate of r-sapphires a-GaN films grown by metal orgamic chemical vapor deposition was etched in molten KOH NaOH for 1.0, 1.5 and 2.0 min. Scanning electron microscope, atomic force microscope, X-ray diffraction and cathodoluminescence was used to study its morphology and defect. We find that etching for 1.5 min at the temperature of 400℃ is appropriate for a-GaN on sapphires substrate. Different from c-GaN which show hexagonal pits, a-GaN shows parallelogram strips. In the direction of c axis it is easier to be etched. That is because the polarity of a-GaN films is anisotropic which leads to different absorption capacities of OH ions in different directions. We also find hexagonal protuberance on the surface which is associated with threading dislocations.