共查询到20条相似文献,搜索用时 171 毫秒
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用卢瑟福背散射/沟道技术研究了1MeVSi ̄+在衬底加温和室温下以不同剂量注入Al_(0.3)G_(0.7)As/GaAs超晶格和GaAs后的晶格损伤。在衬底加温下,观察到Al_(0.3)Ga_(0.7)As/GaAs超晶格和GaAs都存在一个动态退火速率与缺陷产生速率相平衡的剂量范围,以及两种速率失去平衡的临界剂量。超晶格比GaAs更难以损伤,并且它的两种速率失去平衡的临界剂量也大于GaAs中的相应临界剂量,用热尖峰与碰撞模型解释了晶格损伤积累与注入剂量和衬底温度的关系。用CNDO/2量子化学方法计算了GaAs和Al_xGa_(1-x)As中化学键的相对强度,并根据计算结果解释了注入过程中Al_(0.3)Ga_(0.7)As/GaAs超晶格和GaAs中晶格损伤程度的差别。 相似文献
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用深能级瞬态谱(DLTS)和恒温电容瞬态等技术研究了浅杂质注入LEC半绝缘GaAs的γ射线辐照缺陷。在Be-Si共注的LEC半绝缘GaAs中,γ射线辐照引入一电子陷阶E2,并且大大增强了原有的E01(0.298)和E02(0.341)等缺陷,同时明显地瓦解了原有的少子陷阱H03。在单纯注Si的LEC半绝缘GaAs中,γ射线辐阳引进了E'01(0.216),E'02(0.341),E'2,E'4和E'5(0.608)等缺陷。其中E01和E'01是新发现的和γ辐照有关的GaAs缺陷。和低阻衬底同质外延GaAs相比,Be-Si共注LEC半绝缘GaAs具有较低的γ射线辐照缺陷引入率,与此相反,单纯注Si的LEC半绝缘GaAs具有较高的γ射线辐照缺陷的引入率。
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用深能级瞬态谱(DLTS)技术测量了高温退火的Be和Si共注入的LEC半绝缘GaAs(无掺杂)。在多子脉冲作用下的Al/Be-Si共注LECSIGaAs肖特基势垒中,观测到E01(0.298),E02(0.341),E03(0.555)和E04(0.821)等四个电子陷阱以及两个主要的少子(空穴)陷阱H'03(0.54)和H″03(0.57)。两少子陷阱的DLTS信号具有若干特点,比如它们的DLTS·峰难于通过增宽脉冲达到最大高度;以及峰的高度强烈地依赖于温度等。这些现象可以用少子陷阱的少子俘获和热发射理论进行合理地解释。鉴于用DLTS技术测量这种陷阱的困难,我们用恒温电容瞬态技术测定它们的空穴表观激活能分别为0.54和0.57eV。它们是新观测到的和Be-Si共注SIGaAs有关缺陷。
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研究了Gd1-xCaxBa2Cu3O7-y(0.0≤X≤0.20)高温超导体在常压和高压下的超导电性在1-300K温度范围内,利用Bridgman对顶砧获得压力达9.0GPa,测量了(X=0.10,0.15,0.20)样品的dTc/dp分别为7.68,7.8和4.46K/GPa。发现Tc的压力导数随着ca2+含量的增加而下降,分析了氧含量对Tc和dTc/dP的影响.利用常压下晶格参数精修值和阳离子与氧离子间距随压力的改变,说明CuO2面在超导电性上的作用,用CuO2面之间耦合解释Tc(P)曲线的非线性关系。
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采用基于柠檬酸体系的溶胶-凝胶法制备了Pr0.7(Sr1-xCax)0.3MnO3系列的多晶块材, 同时还用脉冲激光沉积技术(PLD)在SrTiO3(100)衬底上外延生长了同一系列的薄膜, 系统研究了它们的晶格结构和电输运行为. 多晶和薄膜样品都具有正交晶格结构, 电输运行为在居里温度TC以上的高温顺磁相都很好
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0.7(Sr1-xCax)0.3MnO3')" href="#">Pr0.7(Sr1-xCax)0.3MnO3
绝热小极化子模型
双交换作用
Jahn-Teller晶格畸变 相似文献
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由于GaAs与AlAs晶格常数相近,GaAs晶格常数为0.56535nm,AlAs的晶格常数为0.56605nm,当固熔体中Al组份x值从0变到1时,晶格常数变化约为0.15%.因此,在GaAs衬底上生长Ga1-xAlxAs时,在界面处的失配位错少,... 相似文献
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高组份Al值的AlxGa1-x As和AlxGa1-x As/GaAs/AlxGa1-xAs/GaAs多层结构的MOCVD生长 总被引:1,自引:1,他引:0
用自制常压MOCVD系统,在半绝缘GaAs衬底上生长高Al组份AlxGa1-xAs(其x值达0.83),和AlxGa1-xAs/GaAs/AlxGa1-xAs/GaAs多层结构,表面镜面光亮。生长层厚度从几十到十几μm可控,测试表明外延层晶格结构完整,x值调节范围宽,非有意掺杂低,高纯GaAs外延层载流子浓度n300K=1.7×1015cm-3,n77K=1.4×1015cm-3,迁移率μ300K=5900cmcm2/V.S,μ77K=55500cm2/V.S。用电子探针,俄歇能谱仪测不出非有意掺杂的杂质,各层间界面清晰平直。 对GaAs,AlGaAs生长层表面缺陷,衬底偏角生长温度及其它生长条件也进行了初步探讨。 相似文献
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Reflection high-energy electron diffraction, atomic force microscopy, transmission electron microscopy, and double-crystal X-ray curves showed that high-quality InAs quantum dot (QD) arrays inserted into GaAs barriers were embedded in an Al0.3Ga0.7As/GaAs heterostructure. The temperature-dependent photoluminescence (PL) spectra of the InAs/GaAs QDs showed that the exciton peak corresponding interband transition from the ground electronic subband to the ground heavy-hole subband (E1-HH1) was dominantly observed and that the peak position and the full width at half maximum corresponding to the interband transitions of the PL spectrum were dependent on the temperature. The activation energy of the electrons confined in the InAs/GaAs QDs was 115 meV. The electronic subband energy and the energy wave function of the Al0.3Ga0.7As/GaAs heterostructures were calculated by using a self-consistent method. The electronic subband energies in the InAs/GaAs QDs were calculated by using a three-dimensional spatial plane wave method, and the value of the calculated (E1-HH1) transition in the InAs/GaAs QDs was in reasonable agreement with that obtained from the PL measurement. 相似文献
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《Superlattices and Microstructures》1998,24(4):299-303
We report on photoluminescence and Raman scattering performed at low temperature (T = 10 K) on GaAs/Al0.3Ga0.7As quantum-well wires with effective wire widths ofL = 100.0 and 10.9 nm prepared by molecular beam epitaxial growth followed by holographic patterning, reactive ion etching, and anodic thinning. We find evidence for the existence of longitudinal optical phonon modes confined to the GaAs quantum wire. The observed frequency at οL10 = 285.6 cm−1forL = 11.0 nm is in good agreement with that calculated on the basis of the dispersive dielectric continuum theory of Enderleinas applied to the GaAs/Al0.3Ga0.7As system. Our results indicate the high crystalline quality of the quantum-well wires fabricated using these techniques. 相似文献
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《Physics letters. A》2001,286(5):332-337
The weak damage induced by 0.8 MeV Si ion implantation in the Al0.25Ga0.75As films epitaxially grown on GaAs substrates was studied by using Rutherford backscattering spectrometry/channeling (RBS/C) and Raman spectroscopy. RBS/C spectra measured from the implanted samples showed rather low damage level induced by the ion implantation with ion dose from 1×1014 to 5×1015 cm−2. The Raman spectra were measured on these samples. Two kinds of phonon modes, GaAs-like and AlAs-like, are observed, which indicate the existence of multiple phonon vibrational modes in the epitaxial Al0.25Ga0.75As films on the GaAs substrate. Compared with the unimplanted sample, the Raman photon peaks for the implanted sample shift gradually to lower energy with the increase of the implantation dose. The strains induced in the implanted layer were also evaluated from the Raman spectra. The result from high resolution double crystal X-ray diffractometry (HRXRD) also verified the evolution of the strains in the implanted layers. 相似文献
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K. H. Park Y. T. Byun Y. Kim S. H. Kim S. S. Choi Y. Chung 《Optical and Quantum Electronics》1995,27(5):363-369
Al0.3Ga0.7As/GaAs/Al0.3Ga0.7As strip-loaded waveguides were fabricated using a broad-beam electron cyclotron resonance (ECR) ion source. It was found that a very smooth etching profile can be obtained by ECR ion etching and the etching rate of Al0.3Ga0.7As is 70 nm min-1. The propagation losses of strip-loaded type III–V compound semiconductor waveguides with various etching depths were studied by the Fabry-Perot cavity method. It was observed that the reflectance at the cleavage increases slightly with etching depth for TE polarization. The propagation loss is measured as 1.5 dB cm-1 for etching depth of 0.7 m, less than 1 dB cm-1 for 0.8 m, and 3.5 dB cm-1 for 1.1 m. 相似文献
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E.M. Goldys H.Y. Zuo T.L. Tansley M.R. Phillips C.M. Contessa 《Superlattices and Microstructures》1998,23(6):1223-1226
Photoluminescence and cathodoluminescence measurements of strained undoped In0.15Ga0.85As/GaAs and In0.15Ga0.85As/Al0.15Ga0.85As quantum well structures with emission lines attributed to the first electron–first heavy hole and first electron–first light hole excitonic transitions have been analysed theoretically within the eight-band effective mass approximation. For In0.15Ga0.85As/GaAs the results are consistent with either type I or type II alignment of the light hole band. In the case of In0.15Ga0.85As/Al0.15Ga0.85As our results indicate type II alignment for the light hole band and offset ratio ofQ = 0.83. 相似文献
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G. Richter W. Stolz P. Thomas S.W. Koch K. Maschke I.P. Zvyagin 《Superlattices and Microstructures》1997,22(4):475-480
The interplay between disorder and electron–electron interaction is studied using measurements of the vertical dc conductivity of intentionally disordered GaAs/Al0.3Ga0.7As superlattices. At low temperatures a quasimetallic behavior is observed even for large disorder which is attributed to an inhomogeneous charge distribution reducing the disorder potential. At low doping levels and low temperatures, exchange–correlation interaction leads to an inhomogeneous charge distribution over the wells of ordered superlattices similar to a one-dimensional Wigner lattice. 相似文献
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N. Syrbu A. Dorogan N. Dragutan T. Vieru V. Ursaki 《Physica E: Low-dimensional Systems and Nanostructures》2011,44(1):202-206
Emission maxima related to the recombination of excitons (e1–hh1, e1–lh1, e2–hh2, and e2–lh2) were observed in photoluminescence spectra of GaAs/In0.3Ga0.7As/GaAs quantum wells. The emission bands due to e1–hh1 and e1–lh1 transitions were found to have a doublet character explained by the exchange interaction of excitons in quantum wells. Emission bands due to radiative Eb–hh1, Eb–lh1 transitions in the buffer GaAs layer are observed in the region of 1.5 eV. 相似文献
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《Superlattices and Microstructures》1993,13(4):459
Hot electron cooling in variously structured and doped quantum wells and superlattices has been studied by low temperature steady-state photoluminescence. A parabolic quantum well realized by thickness grading of Al0.3Ga0.7As and GaAs epitaxial layers deposited by molecular beam epitaxy with electron level spacings of ∼25 meV did not show increased electron plasma temperatures compared to thick epitaxially deposited GaAs or square quantum wells with electron level spacings greater than the LO phonon energy of GaAs; this implies that mechanisms involving intersubband Δk ≠ 0 transitions and interfacial recombination are dominant in the parabolic structure. Investigations as a function of carrier concentration in modulation-doped quantum wells and n-type superlattices with strong miniband formation indicate that increasing the carrier concentration in either structure above ∼ 5 × 1017 cm-3 significantly increases the electron plasma temperatures, even under low light excitation, suggesting that such structures may be suited for high efficiency hot electron photovoltaic and photoelectrochemical cells. 相似文献