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31.
An attempt is made to investigate theoretically the effective electron mass in ternary chalcopyrite semiconductors at low temperatures on the basis of a newly derived dispersion relation of the conduction electrons under cross fields for the more generalized case which occurs from the consideration of the various types of anisotropies in the energy spectrum. It is found, taking degeneraten-CdGeAs2 as an example, that the effective electron mass at the Fermi level along the direction of magnetic quantization depends on both the Fermi energy and the magnetic quantum number due to the combined influence of the crystal field splitting parameter and the anisotropic spin-orbit splitting parameter respectively, resulting in different effective masses at the Fermi level corresponding to different magnetic sub-bands. It is also observed that the same mass at the Fermi level in the direction normal to both magnetic and electric fields also varies both with Fermi energy and magnetic sub-band index, and the characteristic feature of cross-fields is to introduce the index-dependent oscillatory mass anisotropy. The theoretical results are in good agreement with the experimental observations as reported elsewhere. 相似文献
32.
K. P. Ghatak 《Il Nuovo Cimento D》1991,13(10):1321-1324
Summary An attempt is made to formulate the thermoelectric power under strong magnetic quantization (TPM) in superlattices (SLS) of
III–V semiconductors with graded structures and to compare the same with that of the forming materials. It is found, taking
Ga0.8In0.14P0.78Sb0.22/GaAs SL as an example, that the TPM increases with increasing quantizing magnetic field and decreases with increasing electron
concentration respectively in an oscillatory manner. The TPM in SL with graded structures is greater than that of the constituent
bulk materials for III–V SL. 相似文献
33.
K. P. Ghatak A. K. Chowdhury S. Ghosh A. N. Chakravarti 《Applied Physics A: Materials Science & Processing》1980,23(3):241-244
An analytical expression of the modified form of the Einstein relation in heavily doped semiconductors in which Gaussian band
tails are formed near the lower limit of heavy doping is derived for studying the temperature dependence of the diffusivity-mobility
ratio of the carriers in such semiconductors. It is found that, with increasing temperature from relatively low values, the
ratio first increases in a nonlinear manner and then decreases till, at high temperatures, it approaches its value corresponding
to the non-degenerate condition resulting in a peak over a narrow range of temperatures. 相似文献
34.
In order to explain the large pressure dependence of the cubic to tetragonal transition temperature TM in LaAg an expression has been derived from ?TM/?P for a two-fold degenerate electronic band interacting with the tetragonal strain mode. Analogy with the pressure dependence of the ferromagnetic transition temperature Tc in an itinerant system is pointed out. The nature of variation of the superconducting transition temperature with pressure is also discussed. 相似文献
35.
36.
K.P. Ghatak S. Bhattacharya S. Pahari D. De R. Benedictus 《Superlattices and Microstructures》2009,46(3):387-414
We investigate the Einstein relation for the diffusivity-mobility ratio (DMR) for n-i-p-i and the microstructures of nonlinear optical compounds on the basis of a newly formulated electron dispersion law. The corresponding results for III-V, ternary and quaternary materials form a special case of our generalized analysis. The respective DMRs for II-VI, IV-VI and stressed materials have been studied. It has been found that taking CdGeAs2, Cd3As2, InAs, InSb, Hg1−xCdxTe, In1−xGaxAsyP1−y lattices matched to InP, CdS, PbTe, PbSnTe and Pb1−xSnxSe and stressed InSb as examples that the DMR increases with increasing electron concentration in various manners with different numerical magnitudes which reflect the different signatures of the n-i-p-i systems and the corresponding microstructures. We have suggested an experimental method of determining the DMR in this case and the present simplified analysis is in agreement with the suggested relationship. In addition, our results find three applications in the field of quantum effect devices. 相似文献
37.
Nanostructural modifications in a double-graded Pt/Ni/C multi-trilayer, due to irradiation by an energetic ion-beam, have been analyzed using X-ray reflectivity (XRR), X-ray standing wave (XSW) and cross-sectional transmission electron microscopy (X-TEM) techniques. 2 MeV Au2+ ions were rastered on Pt/Ni/C multi-trilayer samples producing a uniformly irradiated area at ion-fluences ranging from 1 × 1014 ions/cm2 to 2 × 1015 ions/cm2. Ion irradiation induced modifications of microstructural parameters, e.g., layer thicknesses and electron densities of individual layers and interface roughnesses have been obtained from XRR analysis. Pt- and Ni-fluorescence yield from the as-deposited sample under the XSW condition show the distinct existence of Pt and Ni layers. The almost indistinguishable Pt- and Ni-fluorescence data over the first order Bragg peak from the sample irradiated at the highest ion-fluence, suggest complete mixing of Pt and Ni. Strong mixing between Pt and Ni in the ion irradiated samples is also corroborated by XRR results. X-TEM studies reveal the individual layer structure in the as-deposited sample. This layer structure is lost in the sample irradiated at the highest ion fluence indicating a complete mixing between Pt and Ni layers and nanoscale grain growth of Pt-Ni alloys. Additionally, formation of Pt-Ni alloy nano-clusters in the C-layers is observed. The results are understood in the light of the positive heat of mixing between Pt and C, and Ni and C and the negative heat of mixing between Pt and Ni. The effect of heat of mixing becomes dominant at high fluence irradiation. 相似文献
38.
K. Westerholt H. Bach S. Methfessel D.K. Ray S.K. Ghatak 《Solid State Communications》1983,45(2):137-140
The magnetic field dependence of the structural transition temperature Tm from the cubic to the tetragonal phase has been determined for single crystals of La3S4 and La3Se4. The observed field dependence of Tm can be accounted for by the band Jahn-Teller model of the coupling of an eg-band to the shear mode of the cubic lattice without invoking any coupling to acoustic or optical phonons. 相似文献
39.
K. P. Ghatak N. Chattopadhyay M. Mondal 《Applied Physics A: Materials Science & Processing》1989,48(4):365-371
An attempt is made to investigate the gate capacitance of MOS structures in n-channel inversion layers on ternary chalcopyrite semiconductors at low temperatures, taking n-channel inversion layers on CdGeAs2 as examples, under both the weak and strong electric field limits, respectively. We have formulated the gate capacitance on the basis of newly derived 2D electron energy spectra for both the limits by considering the various anisotropies of the band parameters within the framework ofk·p formalism. It has been observed that, the gate capacitance increases with increasing surface electric field in an oscillatory manner and the theoretical results are in good agreement with the experimental observations as reported elsewhere. In addition, the corresponding well-known results for n-channel inversion layers on isotropic parabolic semiconductors are also obtained from the generalized expressions derived under certain limiting conditions. 相似文献
40.
An attempt is made to study theoretically, the dependence of the gate capacitance inn-channel inversion larges on ternary chalcopyrite semiconductors on a quantizing magnetic field, takingn-channel inversion layers on CdGeAs2 as an example. It is found, on the basis of a newly derived electron energy spectrum of the above class of semiconductors, that the gate capacitance exhibits spiky oscillations with changing magnetic field and the oscillatory behaviour is in qualitative agreement with the experimental observation reported in the literature for the MOS structure of Hg1–x
Cd
x
Te. 相似文献