Comparison of electrical characteristic between AlN/GaN andAlGaN/GaN heterostructure Schottky diodes * Lü Yuan-Jie(吕元杰) a) , Feng Zhi-Hong(冯志红) a) † , Lin Zhao-Jun(林兆军) b) , Gu Guo-Dong(顾国栋) a) , Dun Shao-Bo(敦少博) a) , Yin Jia-Yun(尹甲运) a) , Han Ting-Ting(韩婷婷) a) , and Cai Shu-Jun(蔡树军) a)