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1.
D. Varshney G. Joshi 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,70(4):523-534
The present paper addresses the high-pressure phase transformation and
mechanical properties of Ga1-xInxAs (x = 0.25, 0.5 and 0.75) by
formulating an effective interionic interaction potential. This potential
consists of the long-range Coulomb and charge transfer caused by the
deformation of the electron shells of the overlapping ions and the
Hafemeister and Flygare type short-range overlap repulsion extended upto the
second neighbor ions and the van der Waals (vdW) interaction. The estimated
values of phase transition pressure and the vast volume discontinuity in
pressure-volume (PV) phase diagram indicate the structural phase transition
from zinc blende (B3) to rock salt (B1). The equation of state curves plotted
between V (P)/ V (0) and pressure are for both the zincblende (B3) and rocksalt
(B1) structures. Further, the variations of the second and third order
elastic constants with pressure have followed a systematic trend, which are
almost identical to those exhibited by the observed data measured for other
compounds of this family. 相似文献
2.
X. W. Zhang J. B. Xia 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,58(3):263-268
The electronic structure, spin splitting energies, and g factors of
paramagnetic In1-xMnxAs nanowires under magnetic and electric
fields are investigated theoretically including the sp-d exchange
interaction between the carriers and the magnetic ion. We find that the
effective g factor changes dramatically with the magnetic field. The spin
splitting due to the sp-d exchange interaction counteracts the
Zeeman spin splitting. The effective g factor can be tuned to zero by the
external magnetic field. There is also spin splitting under an electric
field due to the Rashba spin-orbit coupling which is a relativistic effect.
The spin-degenerated bands split at nonzero kz (kz is the wave
vector in the wire direction), and the spin-splitting bands cross at
kz = 0, whose kz-positive part and negative part are symmetrical. A
proper magnetic field makes the kz-positive part and negative part of
the bands asymmetrical, and the bands cross at nonzero kz. In the
absence of magnetic field, the electron Rashba coefficient increases almost
linearly with the electric field, while the hole Rashba coefficient
increases at first and then decreases as the electric field increases. The
hole Rashba coefficient can be tuned to zero by the electric field. 相似文献
3.
S. Saib N. Bouarissa P. Rodríguez-Hernández A. Muñoz 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,60(4):435-438
We present a theoretical study of the structural properties, namely
lattice constant, bulk modulus and its pressure derivative of zinc-blende
GaxIn1-xN. The calculations are performed using first-principles
calculations in the framework of the density-functional-theory
within the local density approximation under the virtual
crystal approximation. The computed values are in good
agreement with the available experimental data. The composition dependence
of the studied quantities is examined. Besides, the deviation of the alloy
lattice constant from Vegard's law is evaluated. 相似文献
4.
V. N. Mughnetsyan A. A. Kirakosyan 《Journal of Contemporary Physics (Armenian Academy of Sciences)》2008,43(4):173-176
The effect of interdiffusion of aluminum and indium atoms on the exciton emission energy and binding energy in InxGa1?xAs/AlyGa1?yAs quantum dots is studied. It is shown that the emission energy increases monotonically with increasing diffusion length, while the binding energy has a maximum. 相似文献
5.
X. P. Bai S. L. Ban 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,58(1):31-36
A variational method and a memory function approach are
adopted to investigate the electron mobility parallel to the interface for a
model AlxGa1-xAs/GaAs heterojunction and its pressure effect by
considering optical phonon modes (including both of the bulk longitudinal
optical (LO) in the channel side and interface optical (IO) phonons). The
influence of a realistic interface heterojunction potential with a finite
barrier and conduction band bending are taken into account. The properties
of electron mobility versus Al concentration, electronic density and
pressure are given and discussed, respectively. The results show that the
electron mobility increases with Al concentration and electronic density,
whereas decreases with pressure from 0 to 40 kbar obviously. The Al
concentration dependent and the electron density dependent contributions to
the electron mobility from the scattering of IO phonons under pressure
becomes more obvious. The variation of electron mobility with the Al
concentration and electron density are dominated by the properties of IO and
LO phonons, respectively. The effect of IO phonon modes can not be neglected
especially for higher pressure and electronic density. 相似文献
6.
Spacer layer thickness fluctuation scattering in a modulation-doped Al<sub>x</sub>Ga<sub>1-x</sub>As/GaAs/Al<sub>x</sub>Ga<sub>1-x</sub>As quantum well
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We theoretically study the influence of spacer layer thickness fluctuation(SLTF) on the mobility of a twodimensional electron gas(2DEG) in the modulation-doped Al x Ga 1 x As/GaAs/Al x Ga 1 x As quantum well.The dependence of the mobility limited by SLTF scattering on spacer layer thickness and donor density are obtained.The results show that SLTF scattering is an important scattering mechanism for the quantum well structure with a thick well layer. 相似文献
7.
P. Kumar S. Kanakaraju D.L. DeVoe 《Applied Physics A: Materials Science & Processing》2007,88(4):711-714
A study of AlxGa1-xAs as a sacrificial film for surface micromachining is presented. AlxGa1-xAs etch rate and selectivity are measured over a range of aluminum mole fractions and HF etchant concentrations during the
release of structural features up to 500 μm in width. The etch process is found to be diffusion limited, with an inverse power
law relationship between etch depth and etch rate. Excellent selectivity greater than 105 is achieved between sacrificial AlAs and structural GaAs, even for long etches up to 250 μm in length. Compared with previous
studies of AlxGa1-xAs etching for epitaxial liftoff processing, measured etch rates for surface micromachining are approximately an order of
magnitude lower, primarily due to the longer effective etch lengths required. However, unlike epitaxial liftoff, AlxGa1-xAs surface micromachining is compatible with higher HF concentrations which can provide comparable overall etch rates, with
important implications for AlGaAs MEMS fabrication.
PACS 81.05.Ea; 85.85.+j 相似文献
8.
B.-T. Liou 《Applied Physics A: Materials Science & Processing》2007,86(4):539-543
Numerical calculations based on first-principles are applied to study the electronic and structural properties of zincblende
AlxGa1-xN. The results show that the lattice constant has a very small deviation from the linear Vegard’s law. The direct and indirect
bowing parameters of 0.295±0.034 eV and -0.125±0.060 eV are obtained, respectively, and there is a direct-indirect crossover
near x=0.692. Besides, the bulk moduli and their pressure derivatives are monotonically increased with an increase of the
aluminum composition x. The deviation parameter of the bulk modulus of -5.32±1.60 GPa is obtained.
PACS 71.15.-m; 71.15.Nc; 71.55.Eq; 71.20.Nr; 42.70.Qs 相似文献
9.
S.J. Chung B. Karunagaran S. Velumani C.-H. Hong H.J. Lee E.-K. Suh 《Applied Physics A: Materials Science & Processing》2007,86(4):521-524
We have investigated the optical properties of AlxGa1-xN/GaN heterostructures (x=0.08, 0.15, 0.33) grown by metal organic chemical vapor deposition on sapphire using photoluminescence
(PL) and persistent photoconductivity (PPC) measurements. For the AlxGa1-xN/GaN heterostructures (HS) containing high Al composition, we observed an anomalous temperature-dependent photoluminescence
and persistent photoconductivity effects. These results show a strong dependence of the physical properties of AlxGa1-xN/GaN HS on the Al content and layer thickness. The anomalous temperature-dependent PL is usually attributed to the presence
of carrier localization states. These phenomena are explained based on the alloy compositional fluctuations in the AlxGa1-xN/GaN HS. From the PPC measurements, the photocurrent (PC) quenching was observed for AlxGa1-xN/GaN HS and it is explained by the metastable states formed in the underlying GaN layer. Also, the mechanisms behind the
PC quenching and PPC phenomena are explained in detail.
PACS 72.20.Jv; 72.40.+w; 78.55.Cr 相似文献
10.
W. Liu Y. Sun W. Li C.-J. Li F.-Y. Li J.-G. Tian 《Applied Physics A: Materials Science & Processing》2007,88(4):653-656
The properties of Cu(In1-xGax)Se2 (CIGS) thin films obtained by selenization of the precursors with different surface layers have been studied, and photovoltaic
devices based on the absorbers were measured and analyzed. The devices constructed by the absorbers obtained by selenization
of the precursors with CuGa-rich surface layers are improved, compared with those with In-rich surface layers. Through XRD,
SEM, SIMS, illuminated J–V, QE and Raman spectra measurements, it was found that the increased Ga contents within the surface
region of films and the graded Ga distribution can be realized in the selenized thin films fabricated by the precursors with
the CuGa-rich surface layer. Consequently, the performances of the photovoltaic devices based on these thin films are further
improved.
PACS 61.72.Ss; 87.64.Jt; 68.60.Bs; 81.15.Cd; 84.60.Jt 相似文献
11.
The effect of externally introduced variable strains on the polarization properties of quantum-well In28Ga72As/GaAs laser radiation at room temperature is studied experimentally and theoretically. An analysis of the polarization effects at various values of the excess of the working current over the threshold is performed. Data on the energy for the splitting of the levels of light and heavy holes in the quantum well of the structure under consideration are obtained. It is experimentally proven that the effectiveness of the action of a variable strain on the polarization twist substantially increases with increasing quantum well width. 相似文献
12.
Z. Barticevic M. Pacheco C. A. Duque L. E. Oliveira 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,56(4):303-309
A theoretical study, within the effective-mass approximation, of the
effects of applied magnetic fields on excitons in disk-shaped
GaAs-Ga1-xAlxAs quantum dots is presented. Magnetic fields
are applied in the growth direction of the semiconductor
heterostructure. The parity of the excitonic envelope function
related to the simultaneous exchange of ze→-ze and
zh→-zh is a good quantum number and the wave
function, both the odd and even parity, can be expanded as
combination of products of the quantum well electron and hole
function that preserves the parity with appropriate Gaussian
functions. We have simultaneously obtained the energies of the
excitonic ground and excited states and discuss the behavior of
these energies as a function of the magnetic field. 相似文献
13.
Y. Duan G. Tang L. Qin L. Shi 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,66(2):211-215
Elasticity and polarization of GaxAl1-xN alloys subjected
to uniaxial and homogeneous biaxial compression are calculated using
first-principles methods. The uniaxial compression along the c-axis
reduces Young’s modulus along the c-axis, and enhances bulk
modulus and total polarization, whereas the biaxial compression in
the plane perpendicular to the c-axis enhances bulk and Young’s
moduli. It is also found that when the in-plane biaxial compression
is applied by constraining the a-axis lattice constant to that of
AlN, the bulk and Young’s moduli dramatically increase with
increasing Ga concentration, and the total polarization could be
suppressed, even annihilated, and finally enhanced by controlling Ga
concentration. 相似文献
14.
Nishant N. Patel K. B. Joshi 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,59(1):19-23
Using empirical pseudopotential method Γ-L crossover is found for
the Ga0.74Al0.26Sb. The conduction band minimum is observed to
switch at the (0.87, 0, 0) point for Ga0.51Al0.49Sb which shifts to
the X point for Ga0.21Al0.79Sb and remains at X leading finally to
indirect band gap in AlSb. Band structure calculations for a large number of
alloys are performed and bowing parameters bX and bL are proposed
for the EX and EL respectively. Our findings may serve as
directive to select the materials in a range of composition to examine the
bowing parameters and thereby effective mass experimentally for the
GaxAl1-xSb alloys. 相似文献
15.
R. Khordad 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,78(3):399-403
In this work, the diamagnetic susceptibility and the bindingenergy of a hydrogenic donor impurity both in the parabolic andnon-parabolic conduction band models have been calculated withinthe effective mass approximation for a V-grooveGaAs/Ga1- x Al x As quantum wire. According to the resultsobtained from the present work reveals that (i) the value ofdiamagnetic susceptibility due to the non-parabolicity effect ishigher than that of parabolicity effect; (ii) the values ofdiamagnetic susceptibility and binding energy due to thenon-parabolicity effect is not appreciable at low Al molefractions; (iii) the diamagnetic susceptibility approaches to thebulk value both in L \(\rightarrow\) 0 or L \(\rightarrow\) ∞; (iv)the effect of non-parabolocity is not appreciable in the bindingenergy and energy dependent effective mass, for energies lowerthan 50 MeV. 相似文献
16.
We have characterized non-critical phase-matching (NCPM) for both Type I and Type II second harmonic generation (SHG) in y-cut GdxY1-xCOB using a nanosecond optical parametric oscillator (OPO). The variation of the NCPM wavelength with temperature was investigated for different values of the compositional parameter x. Efficient SHG of 1064 nm was achieved by choosing the suitable compositional parameter x=0.28 and by tuning the temperature of the crystal to 52 °C. Using a 25-mm-long Gd0.28Y0.72COB crystal, conversion efficiencies of 41 and 43% were obtained respectively from a mode-locked Nd:YAG and a Q-switched Nd:YAG laser. PACS 42.25.Lc; 42.65.Ky; 42.70.Mp; 42.79.Nv 相似文献
17.
V. Banerjee 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,60(4):493-498
This paper addresses the issues of scaling and self-similarity in typical
nanoparticle films. The role played by microscopic processes contributing to
growth on these issues is probed. While we perform this investigation for a
specific system viz., Pb1-xFexS nanoparticle films for clarity of the
procedures, the analysis is general and can be applied to a variety of systems
obtained using different deposition techniques. 相似文献
18.
First-principles calculations for intrinsic and Zn-doped In0.25Ga0.75As are performed based on density functional theory to study the influence of Zn doping on electronic and optical properties. The band structure, density of state, Mulliken population, dielectric function, complex refractive index, absorption coefficient and reflectivity of In0.25Ga0.75As are calculated. Results show that the Fermi levels of two Zn-doped models enter into the valence bands and Zn atom is more easily to replace In atom than Ga atom. The lattice constant of In0.2344Ga0.75Zn0.0156As reduced after optimization, while that of In0.25Ga0.7344Zn0.0156As increased to the contrary. The Mulliken bond population shows that the doping Zn atoms can enlarge the strength of In–As and Ga–As polar covalent bonds. Furthermore, the calculated absorption coefficient and reflectivity are used to characterize the performance of photoemission, indicates that the photoresponses of Zn-doped models are better than that of the intrinsic. 相似文献
19.
Solid solutions of CdSexTe1-x (0.7x1) were synthesized by vacuum fusion of stoichiometric amounts of CdSe and CdTe constituents in a silica tube. X-ray and electron microscope diffractometry techniques revealed that the CdSexTe1-x thin films were polycrystalline with a hexagonal structure. The variation of lattice constants with composition was found to obey Vegards law. The compositional dependence of the optical constants, the refractive index n and the absorption index k, of the films was determined in the spectral range of 400–2000 nm. The dispersion of the refractive index of the films could be described using the Wemple–DiDomenico single oscillator model. Changes of the dispersion parameters were also studied as a function of the mole fraction x. A plot representing 2=f(h) showed that the CdSexTe1-x thin films of different compositions have two direct transitions corresponding to the energy gaps Eg and Eg+. The variation in either Eg or Eg+ with x indicates that this system belongs to the amalgamation type. The variation follows a quadratic dependence and the bowing parameters were found to be 0.4 and 0.5 eV, respectively. PACS 78.20.-e; 81.15.-z 相似文献
20.
V.C. Selvaraju S. Asokan V. Srinivasan 《Applied Physics A: Materials Science & Processing》2003,77(1):149-153
The I–V characteristics of bulk As40Te60-xSex and As35Te65-xSex glasses have been studied with a current sweep of 0–18 mA-0, over a wide range of compositions (4≤x≤22). All the glasses
studied showed a threshold electrical switching behaviour. The number of switching cycles withstood by the samples has been
found to depend on the ON-state current. It is seen that the switching voltages increase with increase in selenium content.
Further, the switching voltages are found to be almost independent of the thickness of the sample (d), in the range 0.18–0.3 mm.
Also, the switching voltages and the number of switching cycles withstood by the samples are found to decrease with temperature.
Received: 6 November 2002 / Accepted: 8 November 2002 / Published online: 29 January 2003
RID="*"
ID="*"Corresponding author. Fax: +91-80/360-0135, E-mail: sasokan@isu.iisc.ernet.in 相似文献