Ti/Al/Ni/Au在GaN N面上的欧姆接触

以Ti/Al/Ni/Au作为欧姆接触金属体系,通过电感耦合等离子体(ICP)刻蚀的预处理,在氢化物气相外延法生长的单晶氮化镓(GaN)材料的N面实现了良好的欧姆接触,其比接触电阻率为3.7×10-4 Ω·cm2.通过扫描电子显微镜、原子力显微镜、阴极荧光和光致发光谱对GaN N面的表面、光学特性进行了对比表征.结果表明:未刻蚀GaN衬底的N面表面存在一定的损伤层,导致近表面处含有大量缺陷,不利于欧姆接触的形成;而ICP刻蚀处理有效地去除了损伤层.X射线光电子能谱(XPS)分析显示刻蚀后样品的Ga 3d结合能比未刻蚀样品向高能方向移动了约0.3 eV,其肖特基势垒则相应降低,有利于欧姆接触的形成.同时对Fe掺杂半绝缘GaN的N面也进行了刻蚀处理,同样实现了良好的Ti/Al/Ni/Au欧姆接触,其比接触电阻率为0.12 Ω·cm2.

Ohmic Contact of Ti/Al/Ni/Au on N-Face GaN

After pretreatment of inductively coupled plasma (ICP) etching,the Ti/Al/Ni/Au ohmic contact with the specific contact resistivity of 3.7× 10-4 Ω · cm2 was developed on the N-face single crystal GaN substrate grown by hydride vapor phase epitaxy (HVPE).The surface topography and optical properties of the N-face GaN were characterized and compared by scanning electron microscope,atomic force microscope,cathode-luminescence and photoluminescence.The results indicate that the damage layers over N-face of the un-etched GaN sbustrate introduce impurities and defects and hinder the formation of ohmic contact.However,the ICP etching treatment can remove the surface damage layers effectively.X-ray photoelectron spectroscopy (XPS) analysis shows that Ga 3d core level of the etched sample shifts approximately 0.3 eV toward higher binding energy,as compared with the Ga 3d core level of the unetched sample,which indicates a reduction of the Schottky barrier height.The etching treatment is helpful for the formation of ohmic contact.Ti/Al/Ni/Au ohmic contact on N-face of Fe-doped semi-insulating GaN substrate with the etching process also shows good ohmic contact with the specific contact resistivity of 0.12 Ω·cm2.