Development of the Design of Super-Multiperiod Structures Grown by Molecular-Beam Epitaxy and Emitting in the Terahertz Range

Journal of Experimental and Theoretical Physics - A design of terahertz (THz) radiation source has been developed based on an AlGaAs/GaAs superlattice grown by molecular-beam epitaxy. The gain and...     

Admittance Characteristics of nBn Structures Based on Hgcdte Grown by Molecular Beam Epitaxy

Russian Physics Journal - For the first time, the admittance of nBn structures based on HgCdTe grown by molecular beam epitaxy was experimentally investigated in a wide range of frequencies and...     

The Effect of Flow Ratio between Elements of Groups III and V on the Structure and Properties of InGaAs Layers Grown by Low-Temperature Molecular-Beam Epitaxy

InGaAs layers grown by low-temperature molecular-beam epitaxy on InP substrates at variable flow ratios between elements of groups III and V are investigated. Layers with a defect structure and low electrophysical parameters are shown to grow with an excess of the components of group III. Growth with high As flows gives rise to trapping of excess arsenic and generation of point defects (As_III antistructural defects and V_III vacancies). High-quality InGaAs layers at low growth temperatures are produced under near-stoichiometric conditions (V/III = 1–4).     

用MOVPE方法外延生长Si掺杂的立方相GaN

用MOVPE方法采取一种两步生长过程生长了未掺杂和Si掺杂的GaN.在生长了一个20nm厚的缓冲层后,外延生长了1μm厚的立方GaN外延层.利用二次离子质谱测定了掺杂的程度.并用X射线衍射和光致发光测量来表征了未掺杂和Si掺杂GaN的结构和光学质量.     

X射线分析氢化物汽相外延法生长GaN薄膜

氮化物研究在90年代取得显著进步,成功制造出蓝色发光二极管和激光二极管.由于氮化镓与衬底(如:蓝宝石,碳花硅)间存在大的晶格常数和热膨胀系数失配,外延膜中有非常高的位错密度.研究氢化物汽相外延法生长的氮化镓膜中倾斜和扭转现象,并应用到以X射线摇摆曲线的半峰宽计算氮化镓膜中位错密度.Ф扫描曲线表征外延的氮化镓晶体六方对称性,而极图表明氮化镓膜中存在马赛克结构.计算出螺位错密度为:2.93×109cm-2和刃位错密度为:5.25×1010cm-2.     

GaAs-Based Metamorphic Long-Wavelength InAs Quantum Dots Grown by Molecular Beam Epitaxy

A bilayer stacked InAs/GaAs quantum dot structure grown by molecular beam epitaxy on an In0.05Ga0.95As metamorphic buffer is investigated. By introducing a InGaAs：Sb cover layer on the upper InAs quantum dots （QDs） layers, the emission wavelength of the QDs is extended successfully to 1.533 μm at room temperature, and the density of the QDs is in the range of 4× 10^9-8 ×10^9cm^-2. Strong photoluminescence （PL） intensity with a full width at half maximum of 28.6meV of the PL spectrum shows good optical quality of the bilayer QDs. The growth of bilayer QDs on metamorphic buffers offers a useful way to extend the wavelengths of GaAs-based materials for potential applications in optoeleetronic and quantum functional devices.     

Interfaces in InAs/GaSb Superlattices Grown by Molecular Beam Epitaxy

Short period InAs（4ML）/GaSb（SML） superlattices （SLs） with InSb- and mixed-like （or Ga1-xInxAs1-ySby- like） interfaces （IFs） are grown by molecular-beam epitaxy （MBE） on （001） GaSh substrates at optimized growth temperature. Raman scattering reveals that two kinds of IFs can be formed by controlling shutter sequences. X-ray diffraction （XRD） and atomic force microscopy （AFM） demonstrate that SLs with mixed-like IFs are more sensitive to growth temperature than that with InSb-like IFs. The photoluminescence （PL） spectra of SLs with mixed-like IFs show a stronger intensity and narrower line width than with InSb-like IFs. It is concluded that InAs/GaSb SLs with mixed-like IFs have better crystalline and optical properties.     

液相外延生长Cr,Ca∶YAG晶体的光谱特性

由液相外延方法在YAG晶体衬底上得到了可饱和吸收的Cr ,Ca∶YAG晶体外延层 ,给出了Cr,Ca∶YAG晶体外延层在 5 0 0nm～ 15 0 0nm范围内的室温吸收光谱曲线。分析表明 ,由外延方法获得的Cr,Ca∶YAG晶体吸收光谱的主要特征与提拉法晶体基本相同 ,但发现在 75 0nm左右存在一个弱的吸收峰。这个吸收峰极有可能产生于四面体格位的Cr5+ ,可以归属到电偶极容许的2 B1(2 E)→2 B2 (2 T2 )跃迁。     

Semimetal NaaBi Thin Film Grown on Double-Layer Graphene by Molecular Beam Epitaxy

Atomically fiat thin films of topological semimetal Na3Bi are grown on double-layer graphene formed on 6H SiC（0001） substrates by molecular beam epitaxy. By combined techniques of molecular beam epitaxy, scanning tunneling microscopy and angle resolved photoelectron spectroscopy, the growth conditions for NaaBi thin films on double-layer graphene are successfully established. The band structure of NaaBi grown on graphene is mapped along Г-M and Г-K; directions. Furthermore, the energy band of Na3Bi at higher energy is uncovered by doping Cs atoms on the surface.     

Low-Temperature Molecular-Beam Epitaxy of GaAs: Effect of Excess Arsenic on the Structure and Properties of the GaAs Layers

The present paper reviews works devoted to control over the properties of epitaxial GaAs by incorporation of excess (non-stoichiometric) arsenic into the GaAs films grown by molecular-beam epitaxy (MBE) at low-temperature (LT). The effect of excess arsenic on the material structure and properties is analyzed for both as-grown and annealed LT-GaAs layers. The effect of doping on the incorporation of excess arsenic is also examined. The data on the effect of excess arsenic on the properties of the Ga_0.47In_0.53As solid solution are presented. The specific features of the mechanism of the excess arsenic incorporation into the solid phase during the low-temperature epitaxial growth are discussed.     

Dislocation Reduction Mechanisms in Gallium Nitride Films Grown by Canti-Bridge Epitaxy Method

By using the special maskless V-grooved c-plane sapphire as the substrate, we previously developed a novel GaN LEO method, or the so-called canti-bridge epitaxy （CBE）, and consequently wing-tilt-free GaN films were obtained with low dislocation densities, with which all the conventional difficulties can be overcome [J. Vacuum Sci. Technol. B 23 （2005） 2476]. Here the evolution manner of dlslocations in the CBE GaN films is investigated using transmission electron microscopy. The mechanisms of dislocation reduction are discussed. Dislocation behaviour is found to be similar to that in the conventional LEO GaN films except the enhanced dislocation-combination at the coalescence boundary that is a major dislocation-reduction mechanism for the bent horizontal-propagating dislocations in the CBE GaN films. The enhancement of this dislocation-combination probability is believed to result from the inclined shape and the undulate morphology of the sidewalls, which can be readily obtained in a wide range of applicable film-growth conditions during the GaN CBE process. Further development of the GaN CBE method and better crystal-quality of the GaN film both are expected.     

Optimization of Metamorphic InGaAs Quantum Wells on GaAs Grown by Molecular Beam Epitaxy

We investigate the molecular beam epitaxy growth of metamorphic InxGal-xAs materials （x up to 0.5） on GaAs substrates systematically. Optimization of structure design and growth parameters is aimed at obtaining smooth surface and high optical qualdty. The optimized structures have an average surface roughness of 0.9-1.8 nm. It is also proven by PL measurements that the optical properties of high indium content （55%） InGaAs quantum wells are improved apparently by defect reduction technique and by introducing Sb as a surfactant. These provide us new ways for growing device quality metamorphic structures on GaAs substrates with long-wavelength emissions.     

Cr3+离子激活的YAG外延单晶荧光层

Cr3+ 离子掺杂YAG外延层 (Cr3+ ∶YAG)的发光呈宽带谱特征 ,荧光色度坐标为x=0 .6 5 5 1、y =0 .2 949,在CIE1931色度图上相当于主波长λ≈ 6 38nm的红色光 ,并且具有较高的色饱和度 ,其发光谱中引人注目之处还在于荧光主峰的位置均在波长较长的λmax≈ 6 89nm和 70 9nm附近 ,是一种能够实现长波长 (λ≈ 70 0nm)红色光输出的单晶荧光体 ,可用作非晶硅液晶光阀投影仪的高分辨率写入光源。     

Photoemission Studies of the Electronic Structure of GaN Grown by Plasma Assisted Molecular Beam Epitaxy

Physics of the Solid State - The results of experimental studies of the electronic and photoemission properties of the GaN epitaxial layer grown by molecular beam epitaxy with plasma activation of...     

分子束外延生长的极性与非极性BeZnO薄膜的比较研究

采用分子束外延设备在不同晶面蓝宝石衬底上(c面,a面,r面)生长BeZnO薄膜。使用复合缓冲层生长得到了高质量的BeZnO薄膜,X射线衍射半高宽达到600 arcsec。在c面与a面蓝宝石衬底上生长得到了极性BeZnO薄膜,在r面蓝宝石上生长得到了非极性BeZnO薄膜。共振拉曼光谱测试结果表明薄膜中的Be含量在同一水平。相对于c面与a面蓝宝石上的极性BeZnO薄膜,生长在r面蓝宝石衬底上的非极性BeZnO薄膜具有较大的表面粗糙度以及较大的半高宽,但是其光致发光谱中的紫外发光峰远远强于极性BeZnO薄膜,并且黄绿光发光峰弱于极性BeZnO薄膜。     

Epitaxial Properties of Co-Doped ZnO Thin Films Grown by Plasma Assisted Molecular Beam Epitaxy

High quality Co-doped ZnO thin films are grown on single crystalline Al2O3（0001） and ZnO（0001） substrates by oxygen plasma assisted molecular beam epitaxy at a relatively lower substrate temperature of 450℃. The epitaxial conditions are examined with in-situ reflection high energy electron diffraction （RHEED） and ex-situ high resolution x-ray diffraction （HRXRD）. The epitaxial thin films are single crystal at film thickness smaller than 500nm and nominal concentration of Co dopant up to 20%. It is indicated that the Co cation is incorporated into the ZnO matrix as Co^2＋ substituting Zn^2＋ ions. Atomic force microscopy shows smooth surfaces with rms roughness of 1.9 nm. Room-temperature magnetization measurements reveal that the Co-doped ZnO thin films are ferromagnetic with Curie temperatures Tc above room temperature.