氧气氛中p-GaN/Ni/Au电极在相同温度不同合金时间下的欧姆接触形成机制和扩散行为

Abstract

用卢瑟福背散射,沟道技术研究了p-GaN上的Ni/Au电极在氧气氛下相同合金温度(500℃)不同合金时间后的微结构演化,以揭示欧姆接触的形成机制.利用背散射随机谱和RUMP模拟程序研究了电极金属之间的互扩散,用沟道谱探测了电极金属中的氧分布.结合不同合金时间下比接触电阻ρc的变化,发现随着合金时间的延长比接触电阻持续降低,在合金时间60s后降低的速度减慢,Au扩散到GaN的表面,在p-GaN上形成外延结构,O向电极内部扩散反应生成NiO对降低ρc起到了关键的作用,表明合金后Ni/Au双层电极中层反转效应已经发生,这种结构变化是形成欧姆接触的有效机制.在相同合金温度(500℃)不同合金时间中,氧气氛中的p-GaN/Ni/Au电极在合金时间为300 s时形成的欧姆接触效果最佳.

Using Rutherford backscattering (RBS)/channeling method, we investigated the microstructure evolution in oxydizing atmosphere of Ni/Au contact on p-GaN during annealing at constant temperature (500 T) but for different alloying time. The technique of RBS/channeling and simulation of RUMP program were used to investigate the diffusion of the electrode metal. It was found that Ni diffused to the interior of the sample, An diffused to the surface of p-GaN after 60 s alloying time and the epitaxial structures of An also began to form on p-GaN at the same time. The-O also diffused into the sample after 180 s alloying time. Considering a continuous decrease in the rho(c), it is suggested that the epitaxial structures of An on p-GaN and the formation of NiO play a critical role in forming low resistance ohmic contact to p-GaN. At 300 s alloying time at the same annealing temperature (500 degrees C), the epitaxial structure of An was impoved further and the O also diffused deeper into the sample, and the ohmic contact reached the optimal value.