共查询到20条相似文献,搜索用时 140 毫秒
1.
金属有机化合物相外延生长GaN薄膜的电子微结构研究 总被引:1,自引:1,他引:0
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。 相似文献
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高质量GaN外延薄膜的生长 总被引:1,自引:0,他引:1
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(epitaxialylateralovergrowth).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. 相似文献
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GaN外延层中的缺陷对光学性质的影响 总被引:1,自引:1,他引:0
用金属有机化合物气相外延(MOVEP)方法生长具有不同表面形貌的非掺杂GaN,并对部分样品的外延层表面进行镜面加工.用阴极射线发光、光散射和拉曼散射方法观察GaN中深能级发光、缺陷散射光分布和拉曼散射光频移.结果表明,缺陷不但影响GaN的发光和光散射,而且影响拉曼频移 相似文献
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分子束外延高Mg掺杂GaN的发光特性 总被引:2,自引:0,他引:2
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. 相似文献
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结合应变异质界面能带排列的平均键能理论和形变势方法,确定了三种不同衬底上生长的Si/Ge系统在(001)和(110)两种不同晶面上的价带能量不连续值(Ev)得出了Si/Ge系统的Ev值随其衬底Si1-xGex的组分x变化的定量关系结果表明,Si/Ge系统价带平均能量的不连续性(Ev,av)基本不随应变状态的不同而变化,而最高价带的Ev值则表现出对弹性应变的高度敏感性(变化量约达0.5eV),此效应主要来源于单轴应力对价带结构的影响.Si/Ge系统在(001)面和(10)面上的Ev值略有差别,表现出弱的晶格取向的相关性本文对(001)面的计算结果与新近的归一保持赝势方法的大型超原胞计算结果以及相关的实验值相当一致.
关键词: 相似文献
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Liliental-Weber Z Tomaszewicz T Zakharov D Jasinski J O'Keefe MA 《Physical review letters》2004,93(20):206102
The atomic structure of characteristic defects (Mg-rich hexagonal pyramids and truncated pyramids) in GaN:Mg thin films grown with Ga polarity was determined at atomic resolution by reconstruction of the scattered electron wave in a transmission electron microscope. Small cavities within the defects have inside walls covered by GaN of reverse polarity. We propose that lateral overgrowth of the cavities restores matrix polarity on the defect base. From matrix to defect, exchange of Ga and N sublattices leads to a 0.6+/-0.2 A displacement of Ga sublattices. We observe a [1100]/3 shift from matrix AB stacking to BC stacking for the entire pyramid. Electron energy loss spectroscopy detected changes in N edge and presence of oxygen on the defect walls. Our results explain commonly observed decrease of acceptor concentration in heavily doped GaN:Mg. 相似文献
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Engin Tiras Ozlem Celik Selman Mutlu Sukru Ardali Sefer Bora Lisesivdin Ekmel Ozbay 《Superlattices and Microstructures》2012
The two-dimensional (2D) electron energy relaxation in Al0.25Ga0.75N/AlN/GaN heterostructures was investigated experimentally by using two experimental techniques; Shubnikov-de Haas (SdH) effect and classical Hall Effect. The electron temperature (Te) of hot electrons was obtained from the lattice temperature (TL) and the applied electric field dependencies of the amplitude of SdH oscillations and Hall mobility. The experimental results for the electron temperature dependence of power loss are also compared with the current theoretical models for power loss in 2D semiconductors. The power loss that was determined from the SdH measurements indicates that the energy relaxation of electrons is due to acoustic phonon emission via unscreened piezoelectric interaction. In addition, the power loss from the electrons obtained from Hall mobility for electron temperatures in the range Te > 100 K is associated with optical phonon emission. The temperature dependent energy relaxation time in Al0.25Ga0.75N/AlN/GaN heterostructures that was determined from the power loss data indicates that hot electrons relax spontaneously with MHz to THz emission with increasing temperatures. 相似文献
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《Physics letters. A》2019,383(24):3018-3024
In this paper, we have investigated optoelectronic properties of two-dimensional GaN adsorbed with non-metal atoms: H, N and O based on first-principle. We find that adsorption of H, N and O atom on 2D GaN is achieved by chemisorption, and the most stable adsorption site is at the top of N atom. Band structure of 2D GaN after adsorbing H atom moves to low energy region and two-dimensional GaN is transformed into an n-type semiconductor. After adsorption of N atom, a new impurity energy appears at the Fermi level, and N adatom could induce magnetism into 2D GaN. Static dielectric constants of 2D GaN increase and adsorption spectrums have extend to infrared band when adsorbing H and N. Strong reflection peaks and strong adsorption peaks after adsorption are located at deep ultraviolet range, which is beneficial for optoelectronic application in the deep ultraviolet. Specifically, two-dimensional GaN adsorbed with H atom is more conducive to manufacture of nano-optoelectronic devices. 相似文献
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本文利用密度泛函方法,优化了CaN2基态(X2B2)的几何平衡结构,其对称性属于C2v,它的键角、平衡核间距和离解能分别为26.428°,0.2526 nm和9.574 eV.基于量子化学计算得出GaN和GaN2基电子态及其离解极限之后,利用计算数据和最小二乘法得到了GaN的M-S解析势能函数,并计算出各态的谐振频率、力常数和光谱数据.利用多体项展式理论首次得到了GaN2基态的解析势能函数,它准确表达了GaN2的平衡几何结构,在此基础上讨论了Ga N2和N GaN反应系统的反应动力学. 相似文献
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采用电子回旋共振等离子体增强金属有机物化学气相沉积(ECR-PEMOCVD)技术,在c轴取向的蓝宝石即α Al2O3(0001)衬底上,以氮化镓(GaN)缓冲层和外延层作为初始层,分别以高纯氮气(N2)和三甲基铝(TMAl)为氮源和铝源低温生长氮化铝(AlN)薄膜.并利用反射高能电子衍射(RHEED)、原子力显微镜(AFM)和x射线衍射(XRD)等测量结果,研究了氢等离子体清洗、氮化和GaN初始层对六方AlN外延层质量的影响,从而获得解理性与α Al2O3衬底一致的六方相AlN单晶薄膜,其XRD半高宽为1
关键词:
AlN
氢等离子体清洗
氮化
GaN 相似文献
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Two-dimensional growth of GaN thin films on an atomically flat C-face 6H-SiC(0001) surface prepared by ultra-high vacuum Si-etching is observed when using an AlN buffer layer in N plasma-assisted molecular beam epitaxy. Scanning tunneling microscopy and reflection high energy electron diffraction observations reveal a series of Ga-stabilized reconstructions which are consistent with those reported for an N-polar GaN(0001) film. The result, including the effect observed previously for GaN thin film on Si-terminated 6H-SiC(0001), agrees with the polarity assignment of heteroepitaxial wurtzite GaN films on polar 6H-SiC substrates, i.e., GaN film grown on SiC(0001) is <0001> oriented (N-face) while that on SiC(0001) is <0001> oriented (Ga-face). 相似文献
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用局域密度泛函线性丸盒轨道大型超原胞方法(32个原子),对纯纤锌矿结构的GaN用调节计算参数(如原子球与“空球”的占空比)在自洽条件下使Eg的计算值(323eV)接近实验值(35eV).然后以原子替代方式自洽计算杂质能级在Eg中的相对位置.模拟计算了六角结构GaN中自然缺陷以及与C和O有关的杂质能级位置,包括其复合物.计算结果表明,单个缺陷如镓空位VGa、氮空位VN、氧代替氮ON、炭代替氮CN、炭代替镓CGa等与已有的计算结果基本一致.计算结果表明杂质复合物会导致单个杂质能级位置的相对变化.计算了CNON,CGaCN,CNOV和CGaVGa,其中CNON分别具有深受主与浅施主的特征,是导致GaN黄光的一种可能的结构.
关键词:
GaN
杂质能级
电子结构 相似文献
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The drift velocity, electron temperature, electron energy and momentum loss rates of a two-dimensional electron gas are calculated in a GaN/AlGaN heterojunction (HJ) at high electric fields employing the energy and momentum balance technique, assuming the drifted Fermi–Dirac (F–D) distribution function for electrons. Besides the conventional scattering mechanisms, roughness induced new scattering mechanisms such as misfit piezoelectric and misfit deformation potential scatterings are considered in momentum relaxation. Energy loss rates due to acoustic phonons and polar optical phonon scattering with hot phonon effect are considered. The calculated drift velocity, electron temperature and energy loss rate are compared with the experimental data and a good agreement is obtained. The hot phonon effect is found to reduce the drift velocity, energy and momentum loss rates, whereas it enhances the electron temperature. Also the effect of using drifted F–D distribution, due to high carrier density in GaN/AlGaN HJs, contrary to the drifted Maxwellian distribution function used in the earlier calculations, is brought out. 相似文献
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Electronic structure and magnetic properties of substitutional transition-metal atoms in GaN nanotubes 下载免费PDF全文
The electronic structure and magnetic properties of the transition-metal(TM) atoms(Sc–Zn, Pt and Au) doped zigzag GaN single-walled nanotubes(NTs) are investigated using first-principles spin-polarized density functional calculations. Our results show that the bindings of all TM atoms are stable with the binding energy in the range of 6–16 eV. The Sc- and V-doped GaN NTs exhibit a nonmagnetic behavior. The GaN NTs doped with Ti, Mn, Ni, Cu and Pt are antiferromagnetic. On the contrary, the Cr-, Fe-, Co-, Zn- and Au-doped GaN NTs show the ferromagnetic characteristics. The Mn- and Codoped GaN NTs induce the largest local moment of 4μB among these TM atoms. The local magnetic moment is dominated by the contribution from the substitutional TM atom and the N atoms bonded with it. 相似文献
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《Chinese Journal of Physics (Taipei)》2018,56(5):2365-2370
The aluminium gallium nitride (AlGaN) barrier thickness dependent trapping characteristic of AlGaN/GaN heterostructure is investigated in detail by frequency dependent conductance measurements. The conductance measurementsin the depletion region biases (−4.8 V to −3.2 V) shows that the Al0.3Ga0.7N(18 nm)/GaN structure suffers from both the surface (the metal/AlGaN interface of the gate region) and interface (the AlGaN/GaN interface of the channel region) trapping states, whereas the AlGaN/GaN structure with a thicker AlGaN barrier (25 nm) layer suffers from only interface (the channel region of AlGaN/GaN) trap energy states in the bias region (−6 V to −4.2). The two extracted time constants of the trap levels are (2.6–4.59) μs (surface) and (113.4–33.8) μs (interface) for the Al0.3Ga0.7N(18 nm)/GaN structure in the depletion region of biases (−4.8 V to −3.2 V), whereas the Al0.3Ga0.7N (25 nm)/GaN structure yields only interface trap states with time constants of (86.8–33.3) μs in the voltage bias range of −6.0 V to −4.2 V. The extracted surface trapping time constants are found to be very muchless in the Al0.3Ga0.7N(18 nm)/GaN heterostructure compared to that of the interface trap states. The higher electric field formation across the AlGaN barrier causes de-trapping of the surface trapped electron through a tunnelling process for the Al0.3Ga0.7N(18 nm)/GaN structure, and hence the time constants of the surface trap are less. 相似文献