M. S. R. Khan  A. Reza 《physica status solidi (a)》1992,129(1):K11-K16

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Y. Khan 《physica status solidi (a)》1992,130(1):K7-K12

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W. I. Khan 《physica status solidi (a)》1989,112(1):221-227

Theoretical investigations are made to establish the basis for the negative resistances in semiconductor devices. It is possible to show the conditions under which non-linear N- and S-shaped J—E characteristics can exist. The former (N-shaped) characteristics can be derived directly from the transport equations and the nature of positive and negative resistances (or conductances) in a unipolar or bipolar device can be depicted in a classified form in a phase diagram. The latter (S-shaped) can be explained in terms of the mechanisms associated with the deep levels, band to band radiative and non-radiative (Auger effect) transitions. Experimental results on GaAs p⁺-i-n⁺ diodes indicate these characteristics and can hence act as a direct evidence of some of these characteristics.  相似文献   

    

Y. Khan  K. Nahm  M. Rosenberg  H. Willner 《physica status solidi (a)》1977,39(1):79-88

Detailed infrared absorption, superconductivity, and structural investigations are made in the perovskite system BaPb_1–xBi_xO₃ to explain the semiconductor–metal phase transition in this system. It is proposed that the electronic states of Bi³⁺ in BaPb_1–xBi_xO₃ are localized, with a sudden delocalization of them at x = 0·4 where the semiconductor energy gap collapses, thereby giving rise to a Fermi surface with a relatively high density of states in the conduction band at 0 K. It is shown that these materials in the superconducting composition region are type-II s–p superconductors.  相似文献   

    

Y. Khan 《physica status solidi (a)》1974,23(2):425-434

The crystal structures of the RT_y intermetallic compounds, where y = (5n + 4)/(n + 2), n = 0, 1, 2, 3, …, are one-dimensional long-period superstructures of the CaCu₅-type structure, with period, P, given by P = 2(n + 1). The period of these superstructures is related with the valence electron concentration, i.e. number of valence electrons per atom, e/a, as follows: e/a = 1/2 + 1/P. Since the value of e/a, according to this equation, becomes nearly constant for P value greater than eight, RT_y one-dimensional long-period superstructures having periods greater than this value are not likely to exist distinctly. Variation of lattice parameters with composition of RT_y supports this conclusion, too. The equilibrium phase diagram of the Y Co system is presented.  相似文献   

    

M. S. Pathak  S. Khan  S. Ghosh 《physica status solidi b》1984,124(2):489-496

The longitudinal phonon—plasmon interactions in semiconducting plasmas having piezoelectrixc or deformation potential coupling or both (viz. n-InSb) is investigated when the electrons drift in the direction ofthe acoustic wave propagation, in presence of an magnetic field of arbitrary orientation. Using the hydrodynamic approach, the dispersion relation D(Ω, k ) is derived. The conditions for excitation and the gain per radian of the acoustic wave in the collision dominated regime are studied in detail in the quasi-static approximation. The analysis takes into account hot carrier effects and the temperature dependence of the momentum collision frequency. The variation of the gain per radian wih the system parameters is investigated. It is shown that the heating of the carrier decreases the gain.  相似文献   

    

S. Ghosh  S. Khan 《physica status solidi (a)》1984,85(2):535-541

Amplitude modulation as well as demodulation of an electromagnetic wave in a transversely magnetised semiconducting plasma having both, piezoelectric and deformation potential couplings are studied in different wave number regions over a wide range of electron cyclotron frequency. A numerical estimation is made for n-InSb crystal at 77 K.  相似文献   

    

S. Ghosh  S. Khan 《physica status solidi b》1983,119(1):363-373

The interesting nonlinear process of parametric conversion of a high frequency electrostatic wave into an electromagnetic wave is investigated analytically in an n-type piezoelectric semiconductor plasma to which an uniform and static magnetic field is applied along the direction of wave propagation. A general dispersion relation is obtained and solved for both the cases of excited electromagnetic waves (i.e., in the cases of left-hand and right-hand circularly polarized waves) to study the threshold condition and the growth rate of the unstable mode at a pump amplitude well above the threshold. Numerical estimates are made for n-InSb at 77 K irradiated with a large amplitude electron plasma wave of frequency 10¹³ s⁻¹ and wave number 5 × 10⁷ m⁻¹. The threshold electric field is independent of applied magnetic field and the growth rates of the excited modes have linear dependence on the magnetic field.  相似文献   

    

J. L. Deschanvres  C. Millon  C. Jimenez  A. Khan  H. Roussel  B. Servet  O. Durand  M. Modreanu 《physica status solidi (a)》2008,205(8):2013-2017

Divalent ions in a copper oxide matrix M²⁺Cu₂O₂ have been intensively studied for the application field of p‐type transparent conductive oxides (TCOs) in order to achieve transparent electronic devices. In this paper, we are presenting our study of the growth and annealing conditions of SrCu₂O₂ (SCO) thin films deposited by injection metalorganic chemical vapor deposition (MOCVD) apparatus. Limited work has been performed using MOCVD in spite of the high facility to prepare different ratios of precursors, large‐area deposition and high deposition rate. The precursors for this study were strontium and copper tetramethylheptadionate (TMHD) and the solvent used was meta‐xylene. Fourier transform infrared (FTIR) and X‐ray diffraction (XRD) analyses have shown that the as‐deposited films in the temperature range (480–570 °C) were composed of a mixture of copper oxide (CuO) and strontium carbonate (SrCO₃), which is due to the low‐temperature deposition. Post‐deposition treatment was needed to achieve the SCO compound. So, different rapid thermal annealing (RTA) conditions were studied. The RTA under Ar gas is too reductive and metallic copper is clearly visible on the surface. On the other hand, RTA under O₂ partial pressure provokes the combustion of carbonate and the crystallisation of SrCu₂O₃ phase at temperatures above 550 °C as observed by FTIR and XRD measurements. Once this phase is obtained, a final RTA under pure Ar leads to the SCO phase at temperatures higher than 600 °C. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

    

A. Chitnis  V. Adivarahan  J. P. Zhang  M. Shatalov  S. Wu  J. Yang  G. Simin  M. Asif Khan  X. Hu  Q. Fareed  R. Gaska  M. S. Shur 《physica status solidi (a)》2003,200(1):99-101

We report on the development of deep ultraviolet AlGaN multiple quantum well light emitting diodes on sapphire with peak emission wavelength from 278 nm to 340 nm. The high quality of the n⁺‐AlGaN buffer layer was achieved using a new pulsed atomic layer epitaxy growth technique to deposit a high quality AlN buffer layers followed by a strain relief AlN/AlGaN superlattice. These devices exhibited pulsed powers as high as 3 mW, 10 mW and 13 mW for 1 A of pumping current. Under pulsed pumping, the external quantum efficiencies of about 0.1% (278 nm), 0.45% (325 nm) and 0.55% (340 nm) represent record high values and the shortest LED emission wavelengths to date. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献