氧等离子体表面处理对AlGaN/GaN HEMT欧姆接触的影响

采用电感耦合等离子体(ICP)刻蚀系统,研究了氧等离子体表面处理对AlGaN/GaN HEMT欧姆接触电阻的影响。利用能量色散X射线光谱仪、光致发光谱和原子力显微镜以及电学测试设备对处理前后样品进行表征分析。结果表明,在最佳的氧等离子体处理条件(ICP功率250 W,射频功率60 W,压强0.8 Pa,氧气流量30 cm³/min,时间5 min)下,欧姆接触电阻为0.41Ω·mm,比参照样品接触电阻降低了约69%。分析认为经过氧等离子体处理后,在近表面处产生了一定数量的N空位缺陷,这些N空位表现为浅能级施主掺杂,有利于欧姆接触的形成。通过采用氧等离子体表面处理工艺制备的AlGaN/GaN HEMT,在+2 V的栅极偏压下获得了0.77 A/mm的最大漏极饱和电流。

Impact of Oxygen Plasma Surface Treatment on Ohmic Contact of AlGaN/GaN HEMTs

The impact of oxygen plasma surface treatment on ohmic contact resistance of AlGaN/GaN HEMTs was studied by inductively coupled plasma(ICP)etching system.The samples before and after treatment were characterized and analyzed by energy dispersive X-ray spectroscopy,photoluminescence spectrum,atomic force microscopy and electrical testing equipment.The results show that under the optimal oxygen plasma treatment condition(ICP power of 250 W,RF power of 60 W,pressure of 0.8 Pa,O2 flow of 30 cm³/min,time of 5 min),the ohmic contact resistance is 0.41Ω·mm,which is about 69%lower than that of reference samples.Analysis shows that a certain number of N vacancy defects are generated near the surface after oxygen plasma treatment,and the N vacancy appears as shallow level donor doping,which is beneficial to the formation of ohmic contact.The maximum drain saturation current of the AlGaN/GaN HEMT fabricated by oxygen plasma surface treatment is 0.77 A/mm at+2 V gate bias.