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It is shown that the confined impurity state of a semiconductor quantum well develops into an excited impurity band in the case of a superlattice. This is studied by following theoretically the transition from a single to a multiple quantum well or superlattice by exactly diagonalizing the three-dimensional Hamiltonian for a quantum well system with random impurities. Intersubband absorption experiments, which can be nearly perfectly reproduced by the theory, corroborate this interpretation, which also requires reinterpretation of previous data. 相似文献
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The formalism of Matsubara-Toyozawa for impurity bands in semiconductors is extended by including the correlation effect on electron hopping matrix elements. The density of states of impurity bands for various impurity concentrations is computed numerically. The comparison with Matsubara-Toyozawa's result indicates that the impurity bandwidth is drastically reduced by electron correlation. 相似文献
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《Superlattices and Microstructures》2005,37(5):327-332
We have prepared quasi-homoepitaxial Zn0.95Mn0.05O-films on ZnO substrates by pulsed laser deposition. The thin films were characterized by in situ RHEED during growth, X-ray diffraction and reflectometry, as well as transmission electron microscopy (TEM). The magnetic properties have been analyzed by SQUID magnetometry and by measuring the anomalous Hall effect. By varying the growth conditions (substrate temperature: 200–600 ∘C, deposition atmospheres: Ar, O2) a different concentration of impurities has been generated. Our results show that the films are electron doped and exhibit a ferromagnetic coupling that depends on the impurity concentration. 相似文献
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M. D. Medvedev 《Physics of the Solid State》1997,39(2):208-210
The density of one-electron states at the Fermi level with allowance for weak Coulomb correlations between the band electrons
is calculated in a superconductivity model having overlapping wide and flat bands. The dependence of the superconducting transition
temperature on the doping level is obtained.
Fiz. Tverd. Tela (St. Petersburg) 39, 237–239 (February 1997) 相似文献
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The formation of electric field domains in doped semiconductor superlattices is described within a microscopic model. Due to the presence of impurity bands in low-doped samples the current–voltage characteristic is essentially different compared to medium-doped samples. 相似文献
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E. M. Aver’yanov 《Optics and Spectroscopy》2000,89(1):30-36
The features of a static shift and splitting of polarized electronic absorption bands of uniaxial impurity molecules are studied in uniaxial polymer films. The specific properties of the orientation statistics of impurity molecules are found that are typical for stretched polymer films and result in the qualitative difference of the dependence of positions and splitting of polarized absorption bands on the order parameter of the impurity molecules compared to impurity nematic liquid crystals. 相似文献
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Black silicon,produced by irradiating the surface of a silicon wafer with femtosecond laser pulses in the presence of a sulfur-bearing gas,is widely believed to be a potential material for efficient multi-intermediate-band silicon solar cells.Taking chalcogen as an example,we analyse the loss of sunlight for silicon with two impurity bands and we find that loss of the sunlight can be minimized to 0.332 when Te 0 (0.307 eV) and Te + (0.411 eV) are doped into microstructured silicon.Finally,problems needed to be resolved in analysing the relationship between conversion efficiency of the ideal four-band silicon solar cell and the position of the introduced two intermediated bands in silicon according to detailed balance theory are pointed out with great emphasis. 相似文献
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A mathematical formalism for use in the study of the temperature dependence of Tsu-Esaki tunneling currents is developed. The discussion includes recently discovered corrections to the Tsu-Esaki tunneling current calculation. These corrections involve emitter and collector electron density effects. The tunneling current is fully amenable to numerical calculation, but some calculations can be facilitated by analytic techniques. An operator technique of Blankenbecler is illustrated and used to generate low temperature series expansions for the tunneling current and emitter-collector electron densities. 相似文献
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O. V. Alifanov 《Optics and Spectroscopy》2010,108(5):710-713
In terms of the adiabatic approach to determining the states of an impurity dielectric crystal, the temperature dependence
of the first moment (maximum) of the optical band that arises upon vibronic transitions in a local center is studied. It is
shown that the frequency of the band maximum and absolute temperature are linked with each other by a relation that is analogous
to the Wien’s displacement law for equilibrium radiation. This result is consistent with experimental data obtained, in particular
for F absorption and luminescence bands in alkali halide crystals. 相似文献
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A. L. Gurskii 《Journal of Applied Spectroscopy》2000,67(1):111-118
A modification of the model of potential fluctuations is suggested to explain the experimentally observed dependences of the
form and position of the maxima in the impurity luminescence spectra of ZnSe specimens, highly doped with an acceptor nitrogen
impurity, on the degree of doping, excitation level, temperature, and decay time. In this model, analysis of the recombination
of donor-acceptor pairs is replaced by consideration of transitions from localized and delocalized states of the donor impurity
band and density tail of the conduction-band states, which appear in strong doping because of the overlapping of wave functions
of the donor states, to the acceptor levels. The influence of the parameter of the electron-phonon interaction on the spectrum
shape is considered. The model allows one to offer a consistent explanation at the qualitative level for the features observed
experimentally.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 1, pp. 86–90, January–February, 2000. 相似文献