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1.
STRUCTURE STUDY OF MODULATION-DOPED Cd1-xMnxTe: In/CdTe STRAINED LAYER MULTIPLE QUANTUM WELLS
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The photomodulated reflectivity (PR) spectroscopy of modulation-doped diluted mag-netic semiconductor Cd1-xMnxTe: In/CdTe multiple quantum wells has been measured at 20-300K. Several spectral features associated with intersubband transitions have been found. The band structure of Cd1-xMnxTe: In/CdTe has been calculated by the Hartree self-consistent method. The results show that the theory is in agreement with experiments. In addition, an abnormal transition intensity ratio of 22H (the second heavy hole subband to the second electroa subband) to 11H (the first heavy hole subband to the first electron subband) caused by electron filled effect has been reported. At low temperature, a feature associated with Fermi level is observed, which has not been reported before. 相似文献
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《Superlattices and Microstructures》1988,4(1):69-75
Using illustrative examples from the investigations of the author and his collaborators, it is shown that (1) piezo-modulated reflectivity (2) photoluminescence and (3) Raman spectroscopy can be effectively used in the study of collective and localized excitations in semiconductor heterostructures. Results on epilayers of Cd1−xMnxTe:In and ZnSe and quantum well structures of GaAs/AlxGa1−xAs; Cd1−xMnxTe/Cd1−yMnyTe; Cd1−xMnxTe/CdTe; Cd1−xMnxTe:In/CdTe are discussed. 相似文献
3.
E. V. Buzaneva A. P. Vetrov G. D. Popova V. I. Strikha 《Superlattices and Microstructures》1991,10(4)
Atomic and electronic structure modification of a metal-Cd1−xMnxTe interface is achieved using selective etching of the Cd1−xMnxTe surface (x=0, 0.34) and Cd adsorption. It is revealed that Te, TeO2, Mn3O4, and CdTeO3 are formed at the Cd1−xMnxTe surface etched in Br2 solution. Te and Cd1−xMnxTe produce TeCd1−xMnxTe heterojunctions, the salient features of which are nearly symmetric nonlinear I-V characteristics. At the Cd1−xMnxTe surface with adsorbed Cd, CdTe might form, resulting in a CdTe-Cd1−xMnxTe heterojunction. The metal-CdTe-Cd1−xMnxTe microstructure is characterized by a nonlinear dependence of current on voltage and rectifying behaviour. The results obtained give deep insight into electronic processes in metal-Cd1−xMnxTe microstructures. 相似文献
4.
In the present computational study, we have explored the structural, electronic and optical properties of ZnTe, CdTe and HgTe binary compounds and their ternary alloys ZnxCd1-xTe, ZnxHg1-xTe and CdxHg1-xTe as well as their ordered quaternary ZnxCdyHg1-x-yTe alloys using the full potential linearized augmented plane wave (FP-LAPW) method based on the density functional theory. We have numerically estimated the total energies, the lattice parameters, the bulk moduli and their first pressure derivative using the generalized gradient approximation (GGA). The band structure is computed using the modified Becke-Johnson (TB-mBJ) approximation. Results of our study show a nonlinear dependence of the composition on the lattice constant, bulk modulus and band gap for the binary and ternary compounds as well as for the quaternary alloys. Additionally, the dielectric function, the refractive index and the loss energy were also reported. The pressure effect on the band gap energy and optical properties were also investigated and reported. Our results are in good agreement with experimental values and theoretical data available in the literature. 相似文献
5.
《Superlattices and Microstructures》1994,15(3):253
Optical and magneto-optical properties are studied for II-VI semiconductor multiple quantum wells (MQWs) doped with donors in the barriers to give electron concentrations of 2 1010 to 6 1011 cm-2 in the well layers. Following on from the recent identification of negatively charged excitons X- (two electrons bound to one hole) in CdTe/Cd1-xZnxTe MQWs, this paper presents more specifically the circular polarisation of the luminescence associated with X- and with the normal exciton X (one electron and one hole) in this type of structure. Very similar magneto-optical properties are observed for modulation doped Zn0.9Cd0.1Se/ZnSe MQWs, and X- is identified in these wells with a binding energy as large as 7 meV for the second electron at 50Å, well-width. 相似文献
6.
本文对Hg1-xCdxTe的低频吸收带,提出另一种解释。把Hg1-xCdxTe作为具有0—25%Cd(或Hg)替位杂质的HgTe(或CdTe)晶体,用格林函数计算含有一个Cd(或Hg)的HgTe(或CdTe)双原子链振动谱,进而讨论Hg1-xCdxTe混晶振动模的特性,结果表明Hg1-xCdxTe在k→0存在频率不趋于零的声学声子,它们有条件吸收远红外波段的光子,形成低频吸收带。它能说明已报道的实验上观察到的低频吸收带的主要特征,并表明对光学声子存在双模行为的其它混晶,在远红外吸收谱中很可能存在类似的低频吸收带。
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Optical transitions from spin-orbit split-off valence band Γ7 to the conduction band Γ6 were directly observed in transmission measurements on thin samples of CdTe and Cd1?xMnxTe. Precise values of spin-orbit splittings were determined. Giant Zeeman splitting of Γ7 - Γ6 exciton in Cd1?xMnxTe was observed and found coherent with corresponding splitting of Γ8-Γ6 exciton. 相似文献
10.
《Superlattices and Microstructures》1988,4(2):173-180
In this paper, the results of Hg1−xZnxTeCdTe strained layer superlattices grown by MBE are reported, and compared to Hg1−xCdxTeCdTe superlattices. Both Type III and Type I Hg1−xZnxTeCdTe superlattices with different strain have been grown on CdTe(111)B/GaAs(100) and CdTe(100)/GaAs(100) substrates and characterized by electron, X-ray diffraction, infrared transmission and Hall measurements. The values of hole mobility between 5×103 up to 2×104cm2v−1s−1 at T = 23K along (111)B growth orientation and up to 4.9×104cm2v−1s−1 at T = 5K along (100) growth orientation are obtained for Type III superlattices whereas in Type I superlattices, the hole mobility is between 200–300cm2v−1s−1. This drastic change in the hole mobility between Type III and Type I superlattices along with the role of the strain are discussed in this paper. 相似文献
11.
Guo-Long Tan Min Wang Kai Wang Lin Zhang Xue-Feng Yu 《Journal of nanoparticle research》2011,13(11):5799-5807
Cd1−x
Mn
x
Te (x = 0, 0.1, 0.2) nanocrystals have been synthesized by mechanical alloying (MA) Cd, Mn, and Se elemental powders. XRD patterns
and HRTEM images confirmed the formation of cubic Cd1−x
Mn
x
Te nanocrystals. All the diffraction peaks from elemental Cd, Mn, and Te powders disappeared completely in those XRD patterns
of as-milled Cd1−x
Mn
x
Te nanocrystals for more than 20 h. When the MA process was carried out for 40 h, typical zinc blende structure diffraction
mode was exhibited in the XRD pattern. Subsequently, capping the surface of as-milled Cd1−x
Mn
x
Te nanocrystals with long chain trioctylphosphine/trioctylphosphine oxide/nitric acid (TOP/TOPO/NA) molecules has achieved
colorful dispersion solution, which shows similar optical properties to those CdTe nanocrystals prepared by wet chemical process.
The grain size is within the range of 2–8 nm for the capped Cd1−x
Mn
x
Te nanocrystals being ball milled for 40 h. The PL excitation peak red shifts to longer wavelength side with increasing Mn
concentration. Pure CdTe nanocrystals show ferromagnetism behavior at room temperature, the saturation magnetization value
and magnetic hysteresis loop increase with the content of substituting Mn ions within the Cd1−x
Mn
x
Te nanocrystals. 相似文献
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In order to deal with the phenomenon of Cd evaporation during the growth of Cd1-xZnxTe (x=0.1) crystals, Cd compensation was adopted during the growth by adding excess Cd into the raw materials. Photoluminescence (PL) spectra were used to investigate the effects of Cd compensation on the properties of Cd1-xZnxTe. A free exciton (FE) peak appeared in the near band-edge region after Cd compensation, which indicated that the concentration of Cd vacancies (VCd) was reduced in Cd1-xZnxTe crystals by Cd compensation. The donor–acceptor pair (DAP) peak became dominant in the PL spectrum and its first and second order phonon replica could also be easily identified after Cd compensation, which was only a weak hump in the case of Cd1-xZnxTe crystals without Cd compensation. It possibly meant that impurities of Al and In were released from the VCd-related complexes. In addition, the deep energy level transition D peak, decreased obviously after Cd compensation, which confirmed that Cd compensation could reduce the dislocation density effectively. PACS 71.20.Nr; 71.55.Gs; 78.55.-m 相似文献
15.
《Superlattices and Microstructures》1993,13(4):487
Spin-flip Raman spectra have been obtained for two heterostructures, each containing a single CdTe quantum well and a single Cd1-xMnxTe quantum well, with barriers of Cd1-yMnyTe (y>x). The spectra show a clear sensitivity to the thickness of the central barrier between the two wells. The magnitude of the Raman shifts and the resonance energies help identify the origin of the signals in the structures. When the barrier is broad, two signals are observed, one from each separate well. When the width of the barrier is reduced, a single signal is seen, reflecting the coupling of the electronic states of the two wells. The size of the Raman shifts observed also suggest the presence of a low concentration of donors in the material, which modify the form of the electronic wavefunction in the quantum wells. 相似文献
16.
《Superlattices and Microstructures》1994,16(1):1-4
The size quantization of the excitonic polaritons in CdTe/Cd1-xMnxTe (x=0.1) multiple quantum wells was found in reflection and PLE spectra. The series of peaks above the heavy-hole exciton line were observed over a wide energy region in the PLE spectrum and the corresponding structures were seen also in the reflection spectrum. The energies of the peaks agree very well with a simple model of the quantum size effect of the excitonic polaritons. Additionally, subpicosecond time-domain measurements in transient reflectivity revealed oscillatory decay with two frequency components. The frequency difference between these components corresponds to the longitudinal-transverse splitting energy of excitonic polaritons at k=0. 相似文献
17.
《Superlattices and Microstructures》2001,29(3):217-223
The results of empirical pseudopotential calculations for the semiconductor compound Cd1 − xMnxTe are presented. The effective electron and hole masses obtained from the pseudopotential calculations are then employed in an envelope function approximation, using two different effective mass Hamiltonians to evaluate the transition energies of the excitonic ground state in CdTe– Cd1 − xMnxTe quantum wells of variable width. It is shown that in non-magnetic systems it is not possible to utilize exciton energies alone to either distinguish between different model Hamiltonians or to quantify the interface roughness. However, it is shown that the latter can be quantified in magnetic systems via the resulting Zeeman effect. 相似文献
18.
利用X射线粉末衍射方法,在室温高压下观察到了Hg1-xCdxTe(x=0.19)的相变。实验是在DAC高压装置上完成的,压力从0逐步加至10.1 GPa。在常温常压下Hg1-xCdxTe(x=0.19)具有闪锌矿结构。从实验结果看到,在压力为3 GPa和6.8~8.3 GPa之间有两个结构相变存在。初步认为,后一个相变与Hg1-xCdxTe(x=0.19)的金属化有密切关系。通过计算,得到了它在相变前的状态方程,并且与二元HgTe化合物在相变规律上进行了比较。 相似文献
19.
C. R. Becker K. Ortner X. C. Zhang A. Pfeuffer-Jeschke V. Latussek Y. S. Gui V. Daumer H. Buhmann G. Landwehr L. W. Molenkamp 《Physica E: Low-dimensional Systems and Nanostructures》2004,20(3-4):436
The band structure of HgTe quantum wells (QWs) has been determined from absorption experiments on superlattices in conjunction with calculations based on an 8×8 k·p model. The band structure combined with self-consistent Hartree calculations has enabled transport results to be quantitatively explained.Rashba spin–orbit, (SO) splitting has been investigated in n-type modulation doped HgTe QWs by means of Shubnikov–de Haas oscillations (SdH) in gated Hall bars. The heavy hole nature of the H1 conduction subband in QWs with an inverted band structure greatly enhances the Rashba SO splitting, with values up to 17 meV.By analyzing the SdH oscillations of a magnetic two-dimensional electron gas (2DEG) in modulation-doped n-type Hg1−xMnxTe QWs, we have been able to separate the gate voltage-dependent Rashba SO splitting from the temperature-dependent giant Zeeman splitting, which are of comparable magnitudes. In addition, hot electrons and Mn ions in a magnetic 2DEG have been investigated as a function of current.Nano-scale structures of lower dimensions are planned and experiments on sub-micrometer magneto-transport structures have resulted in the first evidence for ballistic transport in quasi-1D HgTe QW structures. 相似文献