蓝宝石衬底上RF-MBE生长的GaN中的极性控制和螺旋位错的降低

摘要

近年来人们报道了用MBE方法生长GaN的飞速进展,利用RF-MBE方法可以获得高的GAN生长速率和高的电子迁移率.本文讨论了用RF-MBE方法在蓝宝石衬底上生长GaN过程中的极性控制和螺旋位错的降低.在充分氮化的蓝宝石衬底上直接生长GaN,使GaN的极性控制为N-极性,并用高温生长的AlN核化层实现GaN的Ga-极性.对于N-和Ga-极性的GaN这两种情况,高温生长的AlN中间迭层的引入,可以有效地抑制螺旋位错的扩散.位错的降低使GaN的室温电子迁移率得到提高,对于Ga-极性的GaN,其值为332cm2/V·s;而对于N-极性的GaN,其值为688cm2/V·s.%As recently remarkable developments for MBE-grown GaN have been reported, a high rngrowth rate of GaN by RF-MBE, and the high electron mobility values could be obtained. The rnpolarity control and the threading dislocation reduction in GaN layers grown on sapphire subrnstrates by RF-MBE are discussed in this paper. The polarity of GaN was controlled to N-polarity rnby growing GaN directly on sufficiently nitrided sapphires, and Ga-polar GaN was realized by utirnlizing the high-temperature-grown A1N nucleation layers. For both N- and Ga-polar GaN, the inrntroducing high-temperature-grown AIN multiple intermediate layers is effective to suppress the rnthreading dislocation propagation. The reduction of dislocation brought about the improved room rntemperature electron mobility, 332cm2/V's for Ga-polar GaN and 688cm2/V's for N-polar GaN.