研究了p型GaN上Pd/NiO/Al/Ni反射电极欧姆接触的比接触电阻率、热稳定性, 以及光学反射率。与传统Pd/Al/Ni电极相比, Pd/NiO/Al/Ni电极的欧姆接触在氮气环境中经300℃下热处理10min后, 仍保持低比接触电阻率(小于5×10-4Ω·cm2)和高反射率(大于80%@365nm)。研究获得的优化Pd/NiO层厚度为1nm/2nm, 此时的Pd/NiO/Al/Ni反射电极既能形成良好的欧姆接触, 拥有低比接触电阻率, 又能减少对紫外光的吸收, 保持高反射率。研究表明适当的NiO层厚度能够有效地防止热处理过程中上层Al金属向p-GaN表面层的渗入, 对于制备高质量的Al基反射电极至关重要。

The specific contact resistance, thermal stability and optical reflectivity of the ohmic contact on p-GaN of Pd/NiO/Al/Ni reflective electrode were investigated. Compared with the traditional Pd/Al/Ni electrode, the ohmic contact of Pd/NiO/Al/Ni electrode keeps low specific contact resistance (＜5×10-4Ω·cm2) and high reflectivity (＞80%@365nm) after annealing at 300℃ for 10 minutes in nitrogen environment. The optimized Pd/NiO layer thickness is 1nm/2nm. Under such conditions, the Pd/NiO/Al/Ni reflective electrode can not only form good ohmic contact, but also have low specific contact resistance, reduce the absorption of UV light and maintain high reflectivity. The results show that the appropriate thickness of NiO layer can effectively prevent the infiltration of the upper layer of Al metal into the surface layer of p-GaN during annealing, which is very important for the preparation of high-quality Al-based reflective electrode.