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1.
Two different ferromagnetic-paramagnetic transitions are detected in (Ga,Mn)As/GaAs(001) epilayers from ac susceptibility measurements: transition at a higher temperature results from (Ga,Mn)As cluster phases with [110] uniaxial anisotropy and that at a lower temperature is associated with a ferromagnetic (Ga,Mn)As matrix with 100 cubic anisotropy. A change in the magnetic easy axis from [100] to [110] with increasing temperature can be explained by the reduced contribution of 100 cubic anisotropy to the magnetic properties above the transition temperature of the (Ga,Mn)As matrix. 相似文献
2.
Keavney DJ Wu D Freeland JW Johnston-Halperin E Awschalom DD Shi J 《Physical review letters》2003,91(18):187203
We report induced Ga and As moments in ferromagnetic Ga(1-x)MnxAs detected using x-ray magnetic circular dichroism at the Mn, Ga, and As L(3,2) edges. Across a broad composition range, we find As and Ga dichroism signals which indicate an As 4s moment coupled antiparallel to the Mn 3d moment, and a smaller parallel Ga 4s moment. The Ga moment follows that of Mn in both doping and temperature dependence. These results are consistent with recent predictions of induced GaAs host moments and support the model of carrier-mediated ferromagnetic ordering involving As-derived valence band states. 相似文献
3.
Elsen M Jaffrès H Mattana R Tran M George JM Miard A Lemaître A 《Physical review letters》2007,99(12):127203
We report on experiments and theory of resonant tunneling anisotropic magnetoresistance (TAMR) in AlAs/GaAs/AlAs quantum wells (QW) contacted by a (Ga,Mn)As ferromagnetic electrode. Such resonance effects manifest themselves by bias-dependent oscillations of the TAMR signal correlated to the successive positions of heavy (HH) and light (LH) quantized hole energy levels in GaAs QW. We have modeled the experimental data by calculating the spin-dependent resonant tunneling transmission in the frame of the 6 x 6 valence-band k.p theory. The calculations emphasize the opposite contributions of the (Ga,Mn)As HH and LH subbands near the Gamma point, unraveling the anatomy of the diluted magnetic semiconductor valence band. 相似文献
4.
ABINIT simulation package with built in local density, generalized gradient, and spin local density approximations was used to investigate the structural, electronic, and magnetic properties of cation mixed (Ga,Mn)(As,N) and (In,Mn)(As,N) quaternaries with equal and fixed compositions of Ga, In, and Mn atoms. In particular, total energy minimization approach was used to compute the equilibrium structural parameters of zinc-blende (GaAs, InAs, and MnAs), wurtzite (GaN, InN, and MnN) binary parent compounds, as well as, the corresponding equilibrium parameters of (Ga,Mn)(As,N) and (In,Mn)(As,N) quaternary systems. The band structures of zinc-blende GaAs, InAs, and MnAs binary parent compounds were computed and analyzed. Spin polarized band structures of the cation mixed (Ga,Mn)(As,N) and (In,Mn)(As,N) quaternaries with equal compositions of Ga, In, and Mn cations were computed and analyzed using spin local density approximation based calculations. Moreover, the magnetic properties of (Ga,Mn)(As,N) and (In,Mn)(As,N) quaternaries with equal concentration of Ga, In, and Mn cations were investigated. Our results suggest that the two quaternary systems are nonmagnetic. An interpretation of our results is presented. In addition, the magnetic properties of (Ga,Mn)N nanocrystal ternaries constructed from doping GaN with one or two Mn atoms were investigated using Vienna Ab-initio Simulation Package (VASP) and compared with those of (Ga,Mn)(As,N) quaternaries. 相似文献
5.
E. I. Malysheva M. V. Dorokhin A. V. Zdoroveyshchev M. V. Ved’ 《Physics of the Solid State》2016,58(11):2271-2276
The spin light-emitting diodes based on InGaAs/GaAs heterostructures with a quantum well and an injector in the form of a (Ga,Mn)As ferromagnetic layer have been studied. It has been demonstrated that the efficiency of electron spin injection in the structure with a (Ga,Mn)As/n+-GaAs tunneling barrier can be controlled by varying the parameters of n+-GaAs. The spin injection control mechanisms associated with the thermal activation and tunneling of carriers have been discussed. 相似文献
6.
Electronic properties and chemical composition of Ge films grown by molecular beam epitaxy on GaAs (110) surfaces were studied in situ by electron energy-loss spectroscopy. The loss peaks involving core-level excitations proved that As atoms segregate at the surface of the growing film. The well known 20 eV loss peak of the clean GaAs (110) surface, being attributed to transitions from Ga(3d) to Frenkel-type excitons of dangling-bond surface states, was found to persist, slightly shifted to 19.7 eV, with the growing Ge (110) film. Since the Ga coverage amounts to below approximately 0.05 of a monolayer this transition seems to contain a strong intraatom contribution. 相似文献
7.
The nonlinear optical properties of a magneto-exciton in a strained Ga_(0.2)In_(0.8)As/GaAs quantum dot 下载免费PDF全文
The magnetic field-dependent heavy hole excitonic states in a strained Ga0.2In0.8As/GaAs quantum dot are investigated by taking into account the anisotropy,non-parabolicity of the conduction band,and the geometrical confinement.The strained quantum dot is considered as a parabolic dot of InAs embedded in a GaAs barrier material.The dependence of the effective excitonic g-factor as a function of dot radius and the magnetic field strength is numerically measured.The interband optical transition energy as a function of geometrical confinement is computed in the presence of a magnetic field.The magnetic field-dependent oscillator strength of interband transition under the geometrical confinement is studied.The exchange enhancements as a function of dot radius are observed for various magnetic field strengths in a strained Ga0.2In0.8As/GaAs quantum dot.Heavy hole excitonic absorption spectra,the changes in refractive index,and the third-order susceptibility of third-order harmonic generation are investigated in the Ga0.2In0.8As/GaAs quantum dot.The result shows that the effect of magnetic field strength is more strongly dependent on the nonlinear optical property in a low-dimensional semiconductor system. 相似文献
8.
《Current Applied Physics》2014,14(8):1063-1066
A ferromagnetic ordering with a Curie temperature of 50 K of fifteen layer of InGaMnAs/GaAs multi quantum wells (MQWs) structure grown on high resistivity (100) p-type GaAs substrates by molecular beam epitaxy (MBE) was found. It is likely that the ferromagnetic exchange coupling of sample with Curie temperature of 50 K is hole-mediated resulting in Mn substituting In or Ga sites. Temperature and excitation power dependent PL emission spectra of InGaMnAs MQWs sample grown at temperature of 170 °C show that an activation energy of Mn ion on the first quantum confinement level in InGaAs quantum well is 36 meV and impurity Mn is partly ionized. It is found that the activation energy of 36 meV of Mn ion in the QW is lower than the activation energy of 110 meV for a substitutional Mn impurity in GaAs. These measurements provide strong evidence that an impurity band existing in the bandgap due to substitutional Mn ions and it is the location of the Fermi level within the impurity band that determines Curie temperature. 相似文献
9.
Migration barriers for diffusion of interstitial Mn in the dilute magnetic semiconductor (Ga,Mn)As are studied using first-principles calculations. The diffusion pathway goes through two types of interstitial sites: As coordinated and Ga coordinated. The energy profile along the path is found to depend on the ratio of concentrations between substitutional and interstitial Mn in GaAs. Two regions of distinctly different behavior, corresponding to n-type and p-type (Ga,Mn)As, are identified. The difference in mobility is a reflection of the change in the charge state of Mn interstitials (double donors) that occurs in the presence of substitutional Mn impurities (acceptors). In addition, substitutional Mn impurities are shown to act as traps for interstitial Mn. The effective migration barrier for the positively doubly charged Mn interstitials in p-type (Ga,Mn)As is estimated to vary from 0.55 to about 0.95 eV. 相似文献
10.
Ortner G Bayer M Lyanda-Geller Y Reinecke TL Kress A Reithmaier JP Forchel A 《Physical review letters》2005,94(15):157401
Controllable interactions that couple quantum dots are a key requirement in the search for scalable solid state implementations for quantum information technology. From optical studies of excitons and corresponding calculations, we demonstrate that an electric field on vertically coupled pairs of In(0.6)Ga(0.4)As/GaAs quantum dots controls the mixing of the exciton states on the two dots and also provides controllable coupling between carriers in the dots. 相似文献
11.
Spacer layer thickness fluctuation scattering in a modulation-doped Al<sub>x</sub>Ga<sub>1-x</sub>As/GaAs/Al<sub>x</sub>Ga<sub>1-x</sub>As quantum well 下载免费PDF全文
We theoretically study the influence of spacer layer thickness fluctuation(SLTF) on the mobility of a twodimensional electron gas(2DEG) in the modulation-doped Al x Ga 1 x As/GaAs/Al x Ga 1 x As quantum well.The dependence of the mobility limited by SLTF scattering on spacer layer thickness and donor density are obtained.The results show that SLTF scattering is an important scattering mechanism for the quantum well structure with a thick well layer. 相似文献
12.
Edmonds KW van der Laan G Farley NR Campion RP Gallagher BL Foxon CT Cowie BC Warren S Johal TK 《Physical review letters》2011,107(19):197601
We report a study of the electronic properties of the ferromagnetic semiconductor (Ga,Mn)As using magnetic linear dichroism in the angular dependence of Mn 2p photoemission under hard x-ray excitation. Bulk plasmon loss satellites demonstrate that the probed Mn ions are incorporated deep within the GaAs lattice, while the observed large dichroism indicates that the spectra originate from ferromagnetic substitutional Mn. Simulations of the spectra using an Anderson impurity model show that the ferromagnetic Mn 3d electrons of substitutional Mn in (Ga,Mn)As are intermediate between localized and delocalized. 相似文献
13.
14.
M. V. Dorokhin A. V. Zdoroveishev E. I. Malysheva Yu. A. Danilov B. N. Zvonkov A. E. Sholina 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2012,6(3):511-514
A self-organized InAs/GaAs quantum dot (QD) array is doped with Mn. The effect of the Mn concentration on the morphology and QD luminescence properties is investigated. It is found that Mn deltadoping of the GaAs buffer layer before QD growth with a layer concentration of 1014 cm?2 leads to the formation of an array of large QDs with variable composition In x Ga1 ? x As. The effect is explained within a model of In and Ga atom interdiffusion. 相似文献
15.
基于密度泛函理论的赝势平面波方法计算了处于填隙位置磁性原子(MnI)对(Ga,Mn) As体系电子结构和磁性的影响. 计算结果表明MnI在GaAs中是施主;代替Ga位的MnGa 与MnI的自旋按反铁磁序排列;静电相互作用使MnGa,MnI倾向于形成MnGa_MnI对. MnI的存在一方面补偿了(Ga,Mn)As中的空穴,降低了空穴浓度;同时还使邻近的MnG a失活. MnI的存在对获得高居里温度的(Ga,Mn)As是极为不利的.
关键词:
(Ga
Mn)As
稀磁半导体
密度泛函理论 相似文献
16.
H.D. Gan H.Z. Zheng J.J. Deng J.F. Bi H. Zhu Y. Ji P.H. Tan F.H. Yang J.H. Zhao 《Solid State Communications》2007,141(8):453-458
A series of (Ga, Mn)As epilayers have been prepared on semi-insulating GaAs (001) substrates at 230 °C by molecular-beam epitaxy under fixed temperatures of Ga and Mn cells and varied temperatures of the As cell. By systematically studying the lattice constants, magnetic and magneto-transport properties in a self-consistent manner, we find that the concentration of As antisites monotonically increases with increasing As flux, while the concentration of interstitial Mn defects decreases with it. Such a trend sensitively affects the properties of (Ga, Mn)As epilayers. 相似文献
17.
Moiseev K. D. Kudryavtsev Yu. A. Charikova T. B. Lugovykh A. M. Govorkova T. E. Okulov V. I. 《Physics of the Solid State》2018,60(12):2402-2407
Physics of the Solid State - Characteristic effects of magnetic ordering and conduction in semiconductor heterostructures with a GaAs : Be/Ga0.84In0.16As/GaAs quantum well and manganese... 相似文献
18.
19.
The interaction between exciton and confined longitudinal optical (LO) phonons, interface optical (IO) phonons in an asymmetric Ga 1 x Al x As/GaAs/Ga 0.7 Al 0.3 As square quantum well is investigated. By applying the LLP-like transformation and variational approach, the numerical results are obtained as functions of the well width and asymmetric-degree of well. The exciton-optical phonons interaction-energy has a minimum value with the increase of the well width. It is demonstrated that the LO-phonon energ... 相似文献
20.
Polaronic effects on the energy levels of a double donor impurity in quantum wells in the presence of a magnetic field 总被引:3,自引:0,他引:3
Zi-xin Liu Zhen-jiang Lai Yong-chang Huang Ya Liu Guo-jun Cheng 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,12(3):347-350
In the presence of a magnetic field the Hamiltonian of the single or double polaron bound to a helium-type donor impurity
in semiconductor quantum wells (QWs) are given in the case of positively charged donor center and neutral donor center. The
couplings of an electron and the impurity with various phonon modes are considered. The binding energy of the single and double
bound polaron in AlxlGa 1-xlAs/GaAs/AlxrGa 1-xrAs QWs are calculated. The results show that for a thin well the cumulative effects of the electron-phonon coupling and the
impurity-phonon coupling can contribute appreciably to the binding energy in the case of ionized donor. In the case of neutral
donor the contribution of polaronic effects are not very important, however the magnetic field significantly modifies the
binding energy of the double donor. The comparison between the binding energies in the case of the impurity placed at the
quantum well center and at the quantum well edge is also given.
Received 16 February 1999 相似文献