氧化Au/Ni/p-GaN欧姆接触形成的机理

Investigation on Mechanism of Oxidized Au/Ni/p-GaN Ohmic Contact

用卢瑟福背散射(RBS)和同步辐射X射线衍射(XRD)研究了p-GaN上的Ni/Au电极在空气下不同温度合金后的微结构的演化,并揭示这种接触结构的欧姆接触形成机制.研究不同温度下比接触电阻(ρc)的变化,发现从450℃开始Au扩散到GaN的表面在p-GaN上形成外延结构以及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.在500℃时,Au的外延结构进一步改善,O进一步向样品内部扩散生成NiO,ρc也达到了最低值.但当合金温度升高到600℃时,金属半导体界面NiO的大部分或全部向外扩散,从而脱离与pGaN的接触,使ρc显著升高.

By synchrotron X-ray diffraction (XRD) and Rutherford back scattering(RBS),the microstructure evolution of oxidized Ni/Au contact to p-GaN annealed at different temperature in air are investigated.Considering a sharp decrease in the ρ c after 450℃-annealing,it is suggested that the epitaxial structures of Au on p-GaN and the formation of NiO play a critical role in forming low resistance Ohmic contact to p-GaN.At 500℃,the epitaxial structure of Au is improved further and the O also diffuses dipper into the samples.At the same time,the ρ c get the lowest value.At 600℃,the O begin to diffuse outwards,so it is implied that most or all of the NiO in the metal-semiconductor inerface begin to diffuse outwards at this temperature.Therefore,it shows that the degradation of Ohmic contact for oxidized Ni/Au is related to the full outdiffusion of the NiO in the metal-semiconductor interface,which causes NiO detached from p-GaN.