氮化镓薄膜中LO声子—等离子体激元耦合模拉曼光谱研究

对生长在蓝宝石衬底上不同Si掺杂浓度的一系列GaN外延膜进行了拉曼散射光谱测量，观察到清晰的LO声子－等离子体激元耕合模的高频支（LPP＋）和低频支（LPP－）及其随掺杂浓度的增加往高频方向的移动，通过进行理论计算和拟合，得到GaN中的等离子体激元的频率及阻尼常数，并由此计算得到GaN中的载流子浓度和迁移率，与红外反射谱测量得到的数据进行了比较，结果表明，2种光谱方法得到的载流子浓度均与霍耳测量相一致。但迁移率比霍耳迁移率要低，接近杂质散射机制下的漂移迁移率。

RAMAN SPECTROSCOPY STUDY ON LO PHONON-PLASMON COUPLED MODE IN GaN THIN FILMS

A series of Si doped GaN thin films grown on sapphire substrate were measured by Raman spectroscopy. Both high-and low-frequency branches of the longitudinal-optical (LO) phonon and plasmon coupling modes (LPP modes) were resolved. With the increasing of doping level, the LPP mode shifts toward higher frequency. The two branches in each spectrum were independently lineshape-fitted based on scattering analysis, and plasmon frequency and damping constant were obtained, thus the free carrier concentration and mobility could be deduced. The carrier concentration derived from each branch of the single spectrum coincidences with each other, and it is also consistent with infrared (IR) reflection and Hall results. The mobility from the low branch fitting is in agreement with the IR values, and is about half values of the Hall mobility, which is close to the conduction drift mobility in the regime of ionized impurity scattering. The high branch mobility is even smaller, which implies some additional scattering effect.