GaN载流子浓度和迁移率的光谱研究

用红外反射光谱的方法对生长在蓝宝石衬底上的α-GaN外延薄膜的载流子浓度和迁移率进行了研究.通过测量蓝宝石衬底和不同Si掺杂浓度的一系列GaN外延膜的远红外反射谱并进行理论计算和拟合，得到GaN中的声子振动参量和等离子振荡的频率及阻尼常量,并由此计算得到其载流子浓度和迁移率.计算结果,红外方法得到的载流子浓度与Hall测量相一致,但迁移率比Hall迁移率要低约二分之一.同时红外谱与喇曼谱上明显观察到LO声子与等离子体激元耦合模，(LPP)随掺杂浓度的变化. 关键词： α-GaN外延薄膜 红外反射光谱 载流子浓度 迁移率 LO声子与等离子体激元耦合模 Raman光谱

OPTICAL SPECTROSCOPY STUDY ON CARRIER CONCENTRATION AND MOBILITY IN GaN

We have studied the carrier concentration and the mobility in GaN expitaxial thin films deposited on sapphire substrate using infrared reflection spectroscopy. By theoretical calculation and fitting with the experimental IR reflection spectra for a series of Si-doped GaN epilayers and the sapphire substrate, we obtain the phonon vibrating parameters and plasmon frequency and damping constant in GaN. The carrier concentration and mobility have been deduced. The results show that the data for carrier concentration coincide with Hall measurement while the mobility is lower than Hall data by a factor of about 0.5. The variation of the LO phonon-plasmon coupling mode with doping level has been clearly observed. Raman measurement has been performed on the same series of samples, showing that the behavior of the LO phonon-plasmon coupling mode is similar to that in IR measurement.