Ti/Al/Ni/Au在GaN N面上的欧姆接触

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

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3.7×10-4Ω·cm^2。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 e V,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0.12Ω·cm^2。

After pretreatment of inductively coupled plasma（ ICP） etching, the Ti/Al/Ni/Au ohmic contact with the specific contact resistivity of 3. 7×10-4Ω·cm2was 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 e V 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·cm^2.