研究了用MOCVD设备在高温和低V/Ⅲ条件下生长的GaN薄膜表面存在的与位错相连的大型V形表面坑,并提出了一个有关质量疏运机制的模型以解释其形成机理.由衬底扩散上出来的Al原子对大型坑的形成具有辅助作用,并阻止了深能级杂质或空位缀饰与坑相连的位错.GaN内的位错是非辐射复合中心,但对深能级发光不起作用.
Large V-shaped pits associated with the dislocation clusters are observed in the surface of GaN thin film grown at relative high temperature or low V／III ratio in MOCVD.A model concerning the mass transport mechanism is put forward to interpret their formation.Al atom diflused from the substrate is found to assist in the formation of the large pit.and to prevent the dislocations connected with the pit from being decorated by the deep level impurities or vacancy.Dislocations in GaN act as nonradiative recombination centers,but do nOt contribute to the deep level Iuminescence.
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