表面处理对AlGaN欧姆接触的影响及机理

Influence and Mechanism of Surface Treatment on Ohmic Contacts to AlGaN Surface

研究了溶液表面处理对AlGaN欧姆接触的影响及机理。用氟硝酸(HNO3+HF)、稀盐酸(HCl)和硫代乙酰胺(CS3CSNH2)溶液处理AlGaN表面后,Ti/Al/Ti/Au电极的比接触电阻率有显著的降低。样品表面Ga3d与O1s的X射线光电子能谱(XPS)测试结果显示:氧元素含量明显降低,表明这三种溶液可以有效地去除AlGaN表面氧化层,其中CS3CSNH2效果最佳;Ga3d峰位在表面处理后发生蓝移现象,相当于AlGaN表面处的费米能级向导带一侧移动,使电子在隧穿过程中的有效势垒高度降低。以上两个因素均对优化AlGaN/GaN欧姆接触有十分重要的意义。

Tthe influence of surface treatment on the ohmic contacts to AlGaN/GaN heterostructure is investigated by using different solutions.The specific contact resistivity dramatically decreases after the treatments.To investigate the mechanism of this improvement on ohmic contacts,the chemical properties of the AlGaN/GaN surface are characterized by monitoring the Ga 3d and O1s peaks using X-ray photoelectron spectroscopy（XPS） measurement.The decrease of the oxygen concentration indicates that the solutions can effectively remove oxides from the samples＇ surface,especially CS3CSNH2.The blue shifts of the Ga 3d peaks demonstrate that Fermi level pinning effect at the surface is mitigated after the surface treatment,resulting in the decrease of the effective barrier height for electron tunneling transport.Both these two factors contribute to the formation of high-quality ohmic contacts of Ti/Al/Ti/Au on AlGaN/GaN surface.