共查询到20条相似文献,搜索用时 15 毫秒
1.
The quantum limit behaviour of the magnetoresistance in narrow-gap semiconductors is investigated. The non-parabolicity of the energy dispersion is taken into account in the density of states. Assuming constant level broadening, both the longitudinal and the transverse magnetoresistance obey asymptotic power laws. The exponents in these power laws are found to be larger than in the case of parabolic energy dispersion. 相似文献
2.
An attempt is made to present a simple theoretical analysis of the energy-wave vector dispersion relation of the conduction electrons in heavily doped non-parabolic semiconductors forming band tails. We observe that the complex energy spectrum in doped small-gap materials whose unperturbed conduction band is described by the three band model of Kane is due to the interaction of the impurity atoms in the tail with the spin-orbit splitting constant of the valence band (Δ), For band-gap (Eg)<Δ the imaginary part predominates which tails in to the conduction band. For the opposite inequality the real part comes in to play which tails in to the split-off band. In the absence of the band tailing effect, the imaginary part of the complex energy spectrum vanishes and the same is also true for doped two-band Kane-type and parabolic energy bands respectively. The present formulation helps us in investigating the Boltzmann transport equation dependent transport properties of degenerate semiconductors and are expected to agree better with experiments. The well-known results of unperturbed three and two band models of Kane together with wide-gap parabolic energy bands have been obtained as special cases of our generalized analysis under certain limiting conditions. 相似文献
3.
A. N. Chakravarti K. P. Ghatak A. Dhar K. K. Ghosh S. Ghosh 《Applied Physics A: Materials Science & Processing》1981,26(3):165-169
An attempt is made to investigate the effect of size quantization on the diffusivity-mobility ratio of the carriers in ultrathin films of semiconductors having Kane-type nonparabolic energy bands. It is shown, takingn-type InSb as an example, that the ratio oscillates both with increasing film thickness and with increasing carrier concentration under degenerate conditions and remains unaffected otherwise. The corresponding results for parabolic semiconductors are also obtained from the expressions derived. 相似文献
4.
H. Oheda 《Solid State Communications》1980,33(2):203-206
The modulated photocurrent in amorphous semiconductors is studied by solving the rate equations for the trap-limited case on a simplified model. It is clarified that the phase shift consists of two parts. One of them is related with the photocarrier generation processes and the other with the transport processes. The analytical result can explain quantitatively the measured phase shift of amorphous As2Se3. 相似文献
5.
We examine under what conditions phase and amplitude modulations are decoupled in a modulated structure, within a Landau Ginzburg approach. For the general case of a pth order commensurability, the condition for phase amplitude decoupling depends on the leading anharmonic terms in the Landau Ginzburg free energy. For a 2Mth order leading anharmonic term, the case p = 2M is a border line case. For p > 2M, phase and amplitude are decoupled near the disordered-incommensurate transition temperature, while they are not for p < 2M. In the latter case decoupling occurs at lower temperatures. We discuss the case of deuterated thiourea, which exhibits a commensurate pinning for p = 9 at T = 191 K. 相似文献
6.
Summary We study the subband energies in quantum wells and quantum wires in the presence of a parallel magnetic field in non-parabolic
semiconductors, on the basis of a generalized dispersion relation considering all types of anisotropies of the energy-band
parameters within the framework ofk·p formalism, by formulating the respective electron energy spectra. It is found, by takingn-Cd3As2 as an example, that the subband energies are greater for quantum wires and smaller for quantum wells, respectively. The magnetic
field diminishes the above values and the corresponding well-known results for quantum-confined parabolic semiconductors have
also been obtained from our generalized expressions under certain limiting conditions. 相似文献
7.
A. N. Chakravarti 《Czechoslovak Journal of Physics》1975,25(7):778-784
The theory of electron diffusion under a temperature gradient (Soret effect) in degenerate semiconductors having non-parabolic energy bands and spherical constant-energy surfaces is worked out for the first time. An expression is given for the Soret coefficient which may be determined from the knowledge of the energy dependence of the relaxation time and can be related to the thermoelectric power. 相似文献
8.
When light which is weakly modulated in amplitude is scattered from a two-level system a phase-shift occurs. We have calculated this phase-shift for a Lorentzian lineshape, and find it depends strongly on linewidth. Expressions are given which would enable a realistic comparison between theory and experiment to be made. 相似文献
9.
An investigation is made of the influence of band non-parabolicity on the relation between the Fermi energies in the presence and absence of magnetic quantization in degenerate semi-conductors through derivation of a simplified form of the relation.On leave of absence from theDept. of Physics, B. N. College, Patna University, Patna 800004. 相似文献
10.
11.
We apply Lindstedt's method and multiple scale perturbation theory to analyze spatio-temporal structures in nonlinear Schr?dinger equations and thereby study the dynamics of quasi-one-dimensional Bose-Einstein condensates with mean-field interactions. We determine the dependence of the amplitude of modulated amplitude waves on their wave number. We also explore the band structure of Bose-Einstein condensates in detail using Hamiltonian perturbation theory and supporting numerical simulations. 相似文献
12.
《Solid State Communications》1987,64(3):361-365
Reflectivity and modulated reflectivity spectra are simulated at the fundamental edge of semiconductors when the back surface of the crystal is taken into account. It is demonstrated that this could give rise to important additional structures, frequently observed but only qualitatively interpreted in most cases. Some expected shapes are presented, arising from direct or indirect absorption with exciton formation. Even if back reflection effects are undesirable in reflectivity experiments, some interesting information could easily be extracted from the spectra, especially for the indirect exciton case. 相似文献
13.
为探讨调频场导致的量子效应的物理本质,运用密度矩阵方程和布洛赫矢量模型,对调频场作用下二能级原子系统中的粒子布居几率振荡现象进行了理论分析,讨论了光场调制振幅对振荡过程的影响。理论计算结果表明,光场调制振幅对粒子布居转移和几率振荡有较大的调制作用。当其他参量不变时,随着调制振幅的增大,粒子布居几率振荡减弱,布居转移效率增高,吸收增强。布洛赫矢量分析表明,该振荡过程是系统粒子数转移、吸收和极化三者之间的动态变化过程。 相似文献
14.
15.
S. Ghosh M.P. Rishi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,20(2):275-279
Using hydrodynamical model of semiconductor plasma analytical investigations are made for the amplitude modulation as well
as demodulation of an electromagnetic wave in a transversely magnetised acousto-optic semiconducting plasma. The inclusion
of carriers diffusion adds new dimension in the analysis presented here. Analysis are made under different wave number regions
over a wide range of cyclotron frequency. It has been seen that diffusion of charge carriers modifies amplitude modulation
and demodulation processes effectively. Numerical estimations are made for n-InSb crystal irradiated by pump wave of frequency 1.6 T s-1. Complete absorption of the waves takes place in all the possible wave lengths regimes when the cyclotron frequency becomes exactly equal to (v
2 + )1/2.
Received 28 February 2002 Published online 19 July 2002 相似文献
16.
本文对光折变晶体中高速调制光简并四波混频过程的特性进行了理论分析、给出了在Ce:SBN晶体中进行的实验结果;并指出,光折变晶体中的简并四波混频可应用于消空间畸变的时域编码通信和双向时域信息的传输、放大。 相似文献
17.
S.K. Biswas A.R. Ghatak A. Neogi A. Sharma S. Bhattacharya K.P. Ghatak 《Physica E: Low-dimensional Systems and Nanostructures》2007,36(2):163-177
We study theoretically the thermoelectric power in the presence of a large magnetic field (TPM) in heavily doped III–V, II–VI, PbTe/PbSnTe, strained layer and HgTe/CdTe quantum dot superlattices (QDSLs) with graded structures on the basis of newly formulated electron energy spectra and compare the same with that of the constituent materials. It has been found, taking heavily doped GaAs/Ga1−xAlxAs, CdS/CdTe, PbTe/PbSnTe, InAs/GaSb and HgTe/CdTe QDSLs as examples, that the TPM increases with increasing inverse electron concentration and film thickness, respectively, in different oscillatory manners and the nature of oscillations is totally band structure dependent. We have also suggested the experimental methods of determining the Einstein relation for the diffusivity–mobility ratio, the Debye screening length and the electronic contribution to the elastic constants for materials having arbitrary dispersion laws. 相似文献
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19.
The model which reproduces accurately and conveniently the waveform of the amplitude modulated cw laser light in the TEM00 mode by a mechanical chopper is developed. It is found that its predictions are in good agreement with the strict, completely accurate but rather lengthy and inconvenient treatment and with the experiment. The criterion for the efficient amplitude modulation of the laser light by a mechanical chopper is formulated. 相似文献
20.
Summary We study the electronic contribution to the second- and third-order elastic constants in strained quantum wire superlattices
of non-parabolic semiconductors with graded structures and compare the same with the constituent materials, by formulating
the appropriate dispersion laws. It is found, taking InSb/GaSb quantum wire superlattice as an example, that the said contributions
increase with decreasing thickness and with increasing electron concentration in oscillatory manners together with the fact
that the influence of the finite interface width enhances their numerical values. An experimental method is suggested for
determining the electronic contribution to the elastic constants in materials having arbitrary dispersion laws. In addition,
the well-known results for constituent semiconductors in the absence of stress have also been obtained as special cases of
our generalized formulations. 相似文献