InGaN合金中LO声子-等离子激元耦合模的研究  

LO Phonon-Plasmon Coupled Mode in Hexagonal InGaN Alloy

作　　者：王瑞敏[1] 陈光德[1] 

机构地区：[1]西安交通大学理学院,陕西西安710049

出　　处：《光谱学与光谱分析》2009年第1期138-141,共4页Spectroscopy and Spectral Analysis

基　　金：国家自然科学基金项目(10474078);陕西省自然科学基金项目(2004A01)资助

摘　　要：分别采用532,488 nm可见光和325 nm紫外光激发,对金属有机化学气相沉积法在蓝宝石衬底上生长的六方相InGaN/GaN薄膜样品在室温和78 K低温下的拉曼散射谱进行了研究。在可见光激发时,E2模和A1(LO)模的散射信号主要来自GaN层;采用紫外光激发时,A1(LO)模向低频方向移动且共振增强,此散射信号来自InGaN层。在可见光激发的情况下,在A1(LO)模的高频方向观察到一个宽峰,此宽峰为InGaN的LO声子-等离子激元耦合模,根据耦合模频率得到InGaN层中的电子浓度为ne=1.61×1018cm-3。紫外光激发时,没有观察到耦合模,A1(LO)模散射信号主要来自样品表面耗尽层,由此估算样品中的耗尽层宽度大约在40 nm。此外,还对比分析了在室温和78 K低温下LO声子-等离子激元耦合模的散射强度的变化规律,计算了不同温度下等离子激元的屏蔽波矢。这些结论对于了解InGaN材料的基本性质以及氮化物光电器件的开发利用都有重要参考价值。Raman scattering spectra of hexagonal InGaN/GaN film,excited with 532 and 488 nm visible laser lines and 325 nm UV laser line,were investigated at room temperature and 78 K.The sample was grown by metalorganic chemical vapor deposition on a sapphire substrate.Excited with 532 and 488 nm visible laser lines,the E2 and A1（LO） modes were observed at about 571.3 and 736.4 cm^-1,respectively.These scattering signals mainly originate from GaN layer.Excited with 325 nm UV laser line,the E2 mode shifts to 569.7 cm^-1,while A1（LO） mode shifts to 730.3 cm^-1 and resonance is enhanced.These scattering signals originate from InGaN layer.A broad feature at high frequency of A1（LO） mode was observed in spectroscopy excited with visible laser line,and was attributed to the LO phonon-plasmon coupled mode of InGaN layer.The electron concentration of InGaN film determined from the frequency of the coupled mode is ne=1.61×10^18 cm^-3.Excited with 325 nm UV laser light,the LO phonon-plasmon coupled mode is absent,and the scattering signal of A1（LO） mode mainly originates from the surface depletion layer of the sample.The thickness of the surface depletion layer is about 40 nm.Furthermore,the scattering intensities of LO phonon-plasmon coupled mode at room temperature and 78 K were compared and analyzed.The screening wave vectors of plasmon at different temperatures were calculated.At low temperature,the screening wave vector increases,the damping of the plasmon decreases,so the LO phonon-plasmon coupled mode becomes stronger.This work is helpful in understanding the property of InGaN and in developing the optoelectronic devices of nitride.

关 键 词：InGaN合金 拉曼散射光谱 LO声子-等离子激元耦合模 

分 类 号：O433[机械工程—光学工程]