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Author

Kamakhya P. Ghatak

Other affiliations: University of Calcutta
Bio: Kamakhya P. Ghatak is an academic researcher from Jadavpur University. The author has contributed to research in topics: Magnetic field & Electron. The author has an hindex of 20, co-authored 105 publications receiving 1232 citations. Previous affiliations of Kamakhya P. Ghatak include University of Calcutta.


Papers
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Journal ArticleDOI
TL;DR: In this article, the authors studied the Burstein-Moss shift and related properties for degenerate n-type semiconductors forming band-tails, on the basis of a newly formulated electron dispersion law and taking into account the wave vector dependence of the optical matrix element.
Abstract: We study the Burstein–Moss shift and related properties for degenerate n-type semiconductors forming band-tails, on the basis of a newly formulated electron dispersion law and taking into account the wave vector dependence of the optical matrix element. It is observed, taking n-InSb as an example for numerical computations, that the optical activation energy increases with increasing carrier concentration and the present theory exhibits better agreement with experimental findings than that of the conventional approach based on the wave vector independence of the optical matrix element.

47 citations

Journal ArticleDOI
TL;DR: In this paper, an attempt is made to study the effective electron mass in strained layer superlattices of non-parabolic semiconductors with graded structures under sirong magnetic quantization and to compare the same with the bulk specimens of the constituent materials, by formulating the appropriate magneto-dispersion laws.
Abstract: An attempt is made to study the effective electron mass in strained layer superlattices of non-parabolic semiconductors with graded structures under sirong magnetic quantization and to compare the same with the bulk specimens of the constituent materials, by formulating the appropriate magneto-dispersion laws. It is found, taking InAs/GaSb superlattice as an example, that the effective electron mass oscillates with the inverse quantizing magnetic field due to the Shubnikov-de Hass effect. The dependence of the effective mass on the magnetic quantum number in addition to Fermi energy is an intrinsic property of such semiconductor heterostructures. The stress makes the mass quantum number dependent in bulk specimens and even in the presence of broadening, the effective masses in superlattices exhibit significant oscillations with enhanced numerical values from that of the constituent semiconductors. Besides the effective electron masses also increase in an oscillatory way with increasing electron c...

41 citations

Journal ArticleDOI
TL;DR: In this paper, the authors studied the effective electron mass at the Fermi-level on the basis of a newly formulated electron energy spectrum for heavily doped non-parabolic III-V semiconductors forming band-tails, taking n-InSb as an example.
Abstract: We study the effective electron mass at the Fermi-level on the basis of a newly formulated electron energy spectrum for heavily doped non-parabolic III–V semiconductors forming band-tails, taking n-InSb as an example. The investigation on the mass includes both the presence and absence of band-tailing states, in parabolic and non-parabolic energy band structures, respectively. The effective mass exists in the forbidden region, which is impossible without band-tailing effects. The analyses have been carried out for the Fermi-energy and other entities, like screening length and impurity screening potential, respectively. The values of the effective mass with band-tailing states are found much less as compared with in the absence of band-tails. The well-known results for unperturbed two-band model of Kane have also been obtained from our generalized analysis under certain limiting conditions.

36 citations

Journal ArticleDOI
TL;DR: In this paper, an attempt was made to investigate theoretically the effective electron mass in ultrathin films of ternary chalcopyrate semiconductors in the presence of crossed electric and magnetic fields on the basis of a newly derived E-k dispersion relation of the conduction electrons.
Abstract: An attempt is made to investigate theoretically the effective electron mass in ultrathin films of ternary chalcopyrate semiconductors in the presence of crossed electric and magnetic fields on the basis of a newly derivedE-k dispersion relation of the conduction electrons, which includes various types of anisotropies in the energy spectrum. It is found, takingn-CdGeAs2 as an example, that the effective electron mass at the Fermi level depends on the Fermi energy and the magnetic and size quantum numbers, respectively, which is a characteristic feature of cross-fields. It is also observed that the crystal field parameter effectively enhances the numerical magnitude of the effective Fermi level mass. The corresponding results for isotropic parabolic energy bands are also obtained from the expressions derived.

34 citations

Journal ArticleDOI
TL;DR: In this paper, an attempt was made to study the Einstein relation for the diffusivity-mobility ration of the electrons of narrow-gap semiconductors under strong magnetic quantization in accordance with the three-band Kane model by incorporating spin and broadening.

32 citations


Cited by
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Journal ArticleDOI
TL;DR: In this article, a unique morphology of SrTiO 3 nanocubes precipitated on TiO 2 nanowires is successfully synthesized in the form of a thin-film heterojunctioned TiO2 / Sr TiO 3 photocatalyst using facile hydrothermal techniques, and the formation mechanisms of the synthesized photocatalysts are meticulously studied and described.
Abstract: A unique morphology of SrTiO 3 nanocubes precipitated on TiO 2 nanowires is successfully synthesized in the form of a thin-film heterojunctioned TiO 2 / SrTiO 3 photocatalyst using facile hydrothermal techniques. The formation mechanisms of the synthesized photocatalysts are meticulously studied and described. Growth of SrTiO 3 single crystal nanocubes (≈50 nm in width) on anatase polycrystalline nanowires follows an in situ dissolution-precipitation pathway. This is consonant with the classic LaMer model. By analyzing the results of field emission scanning electron microscopy (FESEM), field emission transmission electron microscopy (FETEM), X-ray diffraction (XRD), energy dispersive X-ray (EDX) spectroscopy, X-ray photoelectron spectroscopy (XPS), and UV-vis spectrophotometry, a comprehensive structural and morphological characterization of the photocatalysts is established. FESEM images reveal that the anatase film comprises mainly of nanowires bristles while the tausonite film is primarily made up of nanocube aggregations. In comparison to the respective pristine semiconductor photocatalysts, the heterostructured photocatalyst demonstrates the highest efficiency in photocatalytic splitting of water to produce H 2 , 4.9 times that of TiO 2 and 2.1 times that of SrTiO 3 . The enhanced photocatalytic efficiency is largely attributed to the efficient separation of photogenerated charges at heterojunctions of the two dissimilar semiconductors, as well as a negative redox potential shift in the Fermi level.

278 citations

Patent
29 Sep 1995
TL;DR: In this article, a waveguide with an active medium comprising colloidal quantum dots is claimed, where the quantum dots may be caused to produce luminescence in response to input optical radiation, for example to produce optical amplification or laser radiation.
Abstract: An optical fibre comprises a tubular glass cladding (1) with a central opening (2), filled with a colloidal solution of quantum dots (4) in a support medium (3). The quantum dots may be caused to produce luminescence in response to input optical radiation, for example to produce optical amplification or laser radiation. A waveguide with an active medium comprising colloidal quantum dots is claimed.

260 citations

Journal ArticleDOI
TL;DR: In this article, the authors derived the ratio between mobility and diffusion parameters for a Gaussian-like density of states for a wide range of organic materials (polymers or small molecules) and showed that there is an inherent dependence of the transport in trap-free disordered organic materials on the charge density.
Abstract: The ratio between mobility and diffusion parameters is derived for a Gaussian-like density of states. This steady-state analysis is expected to be applicable to a wide range of organic materials (polymers or small molecules) as it relies on the existence of quasiequilibrium only. Our analysis shows that there is an inherent dependence of the transport in trap-free disordered organic materials on the charge density. The implications for the contact phenomena and exciton generation rate in light emitting diodes as well as channel width in field-effect transistors is discussed.

253 citations

Journal ArticleDOI
Byeong Yun Oh1, Min Chang Jeong1, Doo Soo Kim1, Woong Lee1, Jae Min Myoung1 
TL;DR: In this paper, post-deposition annealing treatment in hydrogen atmosphere for potential transparent conductive oxide (TCO) applications was carried out at 573 K for compatibility with typical display device fabrication processes.

189 citations

Journal ArticleDOI
TL;DR: In this article, the second order nonlinear optical coefficient and energy gap data collected from the literature have been classified and are organized by plotting their respective values, and a corresponding trend and fitting strategy is also demonstrated for the figure of merit (FOM) which is used to rank materials for wavelength conversion efficiency.

154 citations