GaN外延层的拉曼散射研究

ＧａＮ外延层的拉曼散射研究１李国华１韩和相１汪兆平２段树琨３王晓亮（１半导体超晶格国家重点实验室２集成光电子学国家重点联合实验室３半导体材料科学实验室中国科学院半导体研究所北京１０００８３）ＲａｍａｎＳｃａｔｅｒｉｎｇｏｆＧａＮＥｐｉｌａｙｅｒ１Ｌ...     

金属有机化合物相外延生长GaN薄膜的电子微结构研究

研究了金属有机化合物气相外延（ＭＯＶＰＥ）方法在（０００１）氧化铝基底上生长的ＧａＮ薄膜的微结构，目的在于解释ＧａＮ缓冲层在二步法生和过程中的作用及其对外延层晶体质量的影响。在缓冲层中观察到了高密度的结构缺陷，并发现了两种晶体结构（立方和六角）的ＧａＮ。进而对两种结构ＧａＮ的成因进行讨论，并对缓冲层和外延层中结构缺陷的关系进行了研究。     

分子束外延高Mg掺杂GaN的发光特性

采用分子束外延技术在蓝宝石衬底上制备Ｍｇ掺杂的立方相ｐ－ＧａＮ,并对其不同温度下的光致发光光谱进行了研究．实验观察到高Ｍｇ掺杂ＧａＮ中施主受主对发光的反常温度行为．理论分析表明,高Ｍｇ掺杂ＧａＮ中施主受主对的发光受到陷阱与受主间竞争俘获非平衡空穴过程和空穴隧穿输运过程的影响．     

单模石英光纤受激拉曼散射温度特性研究

研究了在不同温度下单模石英光纤的受激拉曼散射光谱,从实验和理论上分析了温度对拉曼散射光谱特性的影响,在脉冲调Q倍频YAG激光的泵浦作用下,获得了石英光纤一级斯托克斯光的拉曼频移、带宽及光强随温度的变化规律.实验表明随着温度的升高,拉曼频移逐渐增大,在一定的温度范围内拉曼频移和温度成线性关系.在相同的泵浦功率作用下,当温度较低时,拉曼光谱的级次较低,低温对高阶斯托克斯光有抑制作用;温度越低其阈值越高;而拉曼光谱的谱线宽度随温度的变化不是线性的,存在一个谱线宽度极大值点.理论和实验表明温度对光纤受激拉曼散射的光谱特性有直接的影响.     

Mg掺杂对AlGaN薄膜特性的影响

利用高精度x射线衍射和拉曼散射光谱，对MOCVD生长的不同Mg掺杂量的AlGaN薄膜的c轴 晶格常数、摇摆曲线和拉曼频移进行测量发现：当Mg掺杂剂量较小时，E2模式向 低频方向漂移表明张力应力有所增加，但是摇摆曲线和A1(LO)模式半高宽减小表 明薄膜质量有所提高；随着Mg掺杂剂量的增加，E2模式反向漂移表明此时薄膜中 存在压力应力，同时薄膜质量有所下降.最后根据拉曼频移和应力改变进行拟合得出相应的 线性表达式为Δσ＝-0298+0562·ΔE. 关键词： AlGaN:Mg 异质外延 x射线衍射 拉曼散射     

MOCVD生长的GaN单晶膜的蓝带发光研究

对实验室用ＭＯＣＶＤ方法生长的未掺杂ＧａＮ单晶膜的发光性能进行了研究。结果表明：在室温时未掺杂ＧａＮ单晶出现的能量为２．９ｅＶ左右蓝带发光与被偿度有较强的依赖关系。高补偿ＧａＮ的蓝带发射强,低补偿ＧａＮ的蓝带发射弱。对蓝带发光机理进行了探讨,认为蓝 导带电子过至受主能级的发光（ｅＡ发光）。观察到降低ＧａＮ补偿度能提高ＧａＮ带边发射强度。     

高质量GaN外延薄膜的生长

综述了高质量ＧａＮ外延薄膜的生长研究工作的最新重要进展．主要采用的新工艺为：在较低温度下生长ＧａＮ缓冲层后再高温生长ＧａＮ外延薄膜,双气流金属有机化合物气相沉积（ＭＯＣＶＤ）,以及用开有窗口的ＳｉＯ２膜截断穿过位错后横向覆盖外延生长（ｅｐｉｔａｘｉａｌｙｌａｔｅｒａｌｏｖｅｒｇｒｏｗｔｈ）．Ｘ射线衍射和高分辨电镜研究证实,上述工艺使ＧａＮ外延薄膜质量得到显著提高．利用这种薄膜研制成的蓝色激光管即将投放市场．     

皮秒激光抽运高压H：的受激拉曼散射研究

利用Nd：YAG锁模序列脉冲激光(1064nm)抽运充有高压H2的拉曼池，输出光束经棱镜分光后投射在屏上，在可见光及近紫外光区用彩色腔卷摄得15个受激拉曼散射光斑；经1m光栅摄谱仪摄谱，在365--605nm波长范围内得到65条受激拉曼谱线．通过实验结果与理论计算值的比较．证明除了H2的振动拉曼频移量4154．6cm^-1外，还有多个振动及转动拉曼频移量共同参与作用，从而产生了从紫外到红外众多渡长的受激拉曼散射光．     

用拉曼散射光谱估算纳米Ge晶粒平均尺寸

用射频共溅射技术和真空退火方法制备了埋入ＳｉＯ２基底中的纳米Ｇｅ复合膜（ｎｃ－Ｇｅ／ＳｉＯ２）测量了不同温度退火后该复合膜的拉曼散射光谱，其结果与晶体Ｇｅ的拉曼谱相比，纳米Ｇｅ的拉曼峰红移峰形变宽，用拉曼谱的参数计算了纳米Ｇｅ晶粒的平均尺寸，所得结果与声子限域理论模型符合。     

皮秒激光抽运高压H2的受激拉曼散射研究

利用NdYAG锁模序列脉冲激光(1064nm)抽运充有高压H2的拉曼池,输出光束经棱镜分光后投射在屏上,在可见光及近紫外光区用彩色胶卷摄得15个受激拉曼散射光斑;经1m光栅摄谱仪摄谱,在365-605nm波长范围内得到65条受激拉曼谱线.通过实验结果与理论计算值的比较,证明除了H2的振动拉曼频移量4154.6cm-1外,还有多个振动及转动拉曼频移量共同参与作用,从而产生了从紫外到红外众多波长的受激拉曼散射光.     

Raman scattering studies on manganese ion-implanted GaN

This paper reports that the Raman spectra have been recorded on the metal-organic chemical vapour deposition epitaxially grown GaN before and after the Mn ions implanted. Several Raman defect modes have emerged from the implanted samples. The structures around 182 cm-1 modes are attributed to the disorder-activated Raman scattering, whereas the 361 cm-1 and 660 cm-1 peaks are assigned to nitrogen vacancy-related defect scattering. One additional peak at 280 cm-1 is attributed to the vibrational mode of gallium vacancy-related defects and/or to disorder activated Raman scattering. A Raman-scattering study of lattice recovery is also presented by rapid thermal annealing at different temperatures between 700°C and 1050°C on Mn implanted GaN epilayers. The behaviour of peak-shape change and full width at half maximum (FWHM) of the A1(LO) (733 cm-1) and E2H (566 cm-1) Raman modes are explained on the basis of implantation-induced lattice damage in GaN epilayers.     

Si基GaN的微结构表征

采用快速辐射加热/低压-金属有机化学气相淀积(RTP/LP-MOCVD)方法分别以AlN和阳极氧化铝为缓冲层材料在Si衬底上外延生长GaN薄膜,通过X射线衍射谱(XRD)、光荧光谱(PL)、拉曼散射谱(RamanScattering)等手段对它们的微结构进行了表征和分析,结果指出AlN是优良的缓冲层材料。     

The influence of substrate etched on the quality of GaN epilayers

We report the growth of GaN epilayers on the sapphire substrate etched by MOCVD. Sapphire substrate is etched by H₃PO₄ and NaOH. The Raman scattering spectroscopy and photoetching analyses show that the substrate etched can effectively decrease the residual stress and the dislocations density in these epilayers. The X-ray diffraction analysis shows the process can reduce the value of the FWHM. Therefore, the quality of GaN epilayers should be improved by substrate etched.     

Raman spectroscopy of optical phonons as a probe of GaN epitaxial layer structural quality

We report on Raman scattering measurements of all Raman-active phonons in wurtzite and zinc blende structure GaN epilayers grown on GaAs (001), GaAs (111)A, and GaAs (111)B oriented substrates by means of molecular beam epitaxy (MBE). Raman spectra are taken from these epilayers at room temperature and 77 K in backscattering geometry. The measured values of the phonon frequencies are in agreement with other studies and with lattice dynamic calculations of phonon modes in GaN zinc blende and wurtzite structures. We show that crystal quality is much better in samples grown on GaAs (111) substrates than in samples grown on GaAs (001) substrates. The observation of disorder-activated modes gives information about sample quality. Comparison of the spectra from different thickness epilayers shows that the GaN is more highly disordered close to the substrate, particularly for the (001) substrates. Received 16 July 1999     

初始化生长条件对a-GaN中应变的影响

利用高分辨X射线衍射(HRXRD)与拉曼散射光谱(Raman scattering spectra)研究了氮化处理与低温AlN缓冲层对低压金属有机化学气相沉积(LP-MOCVD)在r面蓝宝石衬底上外延的a面GaN薄膜中的残余应变的影响。实验结果表明:与氮化处理后生长的a-GaN相比,使用低温AlN缓冲层后生长的a-GaN具有较小的摇摆曲线的半高宽和较低的残余应变,而且其结构各向异性和残余应变各向异性也均有一定程度的降低。因此,与氮化处理相比,低温AlN缓冲层更有利于a-GaN的生长。     

Comparative study of different properties of GaN films grown on(0001) sapphire using high and low temperature AlN interlayers

Comparative study of high and low temperature AlN interlayers and their roles in the properties of GaN epilayers prepared by means of metal organic chemical vapour deposition on(0001) plane sapphire substrates is carried out by high resolution x-ray diffraction,photoluminescence and Raman spectroscopy.It is found that the crystalline quality of GaN epilayers is improved significantly by using the high temperature AlN interlayers,which prevent the threading dislocations from extending,especially for the edge type dislocation.The analysis results based on photoluminescence and Raman measurements demonstrate that there exists more compressive stress in GaN epilayers with high temperature AlN interlayers.The band edge emission energy increases from 3.423 eV to 3.438 eV and the frequency of the Raman shift of E2(TO) moves from 571.3 cm 1 to 572.9 cm 1 when the temperature of AlN interlayers increases from 700 C to 1050 C.It is believed that the temperature of AlN interlayers effectively determines the size,the density and the coalescence rate of the islands,and the high temperature AlN interlayers provide large size and low density islands for GaN epilayer growth and the threading dislocations are bent and interactive easily.Due to the threading dislocation reduction in GaN epilayers with high temperature AlN interlayers,the approaches of strain relaxation reduce drastically,and thus the compressive stress in GaN epilayers with high temperature AlN interlayers is high compared with that in GaN epilayers with low temperature AlN interlayers.     

应力和掺杂对Mg:GaN薄膜光致发光光谱影响的研究

对化学气相沉积(MOCVD)法在宝石衬底上生长的Mg掺杂GaN薄膜的表面及其GaN缓冲层的光致发光(PL)光谱进行了测量，用Raman光谱和x射线衍射(XRD)对GaN薄膜中的应力进行确定，通过PL光谱中的中性束缚激子跃迁能量的变化确定薄膜中应力的影响，从而研究Mg掺杂对p型GaN的DAP跃迁影响规律. 关键词： 光致发光 应力 Raman光谱     

GaN外延层中的缺陷研究

采用阴极射线致发光法观察金属有机物汽相外延法生长的具有不同表面形貌的GaN外延层中黄色发光带的强度分布.结果表明六角金字塔形表面形貌对发光强度分布的测量有很大影响.测量和比较表面镜面加工样品的黄色发光带强度分布、原子序数衬度和X射线波谱发现,黄色发光带的强度在含有O和C等杂质缺陷附近较强.高分辨透射电子显微镜观察表明,杂质缺陷区的晶格结构不同于GaN基质,以及位错和裂缝等由应力引起的缺陷.认为此类缺陷可能是生长过程中,杂质在结晶小丘合并处的V形凹角中的沉积所产生. 关键词：     

STUDY OF MOLECULAR BEAM EPITAXIAL GROWTH AND OPTICAL CHARACTERISTICS OF HgCdTe

HgCdTe epilayers were grown by molecular beam epitaxy on GaAs(211)B substrates. Process of the HgCdTe epitaxial growth can be monitored by reflection high-energy electron diffraction. Results of the infrared transmission spectrum, Raman scattering spectrum and infrared photoluminescence spectrum in magnetic field have been studied.