共查询到20条相似文献,搜索用时 15 毫秒
1.
Janet E. Hails Stuart J.C. Irvine David J. Cole-Hamilton Jean Giess Michael R. Houlton Andrew Graham 《Journal of Electronic Materials》2008,37(9):1291-1302
Acceptor doping of many II–VI compound semiconductors has proved problematic and doping of epitaxial mercury cadmium telluride
(MCT, Hg1−x
Cd
x
Te) with arsenic is no exception. High-temperature (>400°C) anneals followed by a lower temperature mercury-rich vacancy-filling
anneal are frequently required to activate the dopant. The model frequently used to explain p-type doping with arsenic invokes an amphoteric nature of group V atoms in the II–VI lattice. This requires that group VI
substitution with arsenic only occurs under mercury-rich conditions either during growth or the subsequent annealing and involves
site switching of the As. However, there are inconsistencies in the amphoteric model and unexplained experimental observations,
including arsenic which is 100% active as grown by metalorganic vapor-phase epitaxy (MOVPE). A new model, based on hydrogen
passivation of the arsenic, is therefore proposed. 相似文献
2.
A. A. Andronov Yu. N. Nozdrin A. V. Okomel’kov V. S. Varavin N. N. Mikhailov G. Yu. Sidorov 《Semiconductors》2010,44(4):457-462
The main requirements for optimization of the MCT-based (Cd
x
Hg1 − x
Te-based) structures for an increase in the wavelength of the stimulated radiation from them under optical pumping are discussed.
The emergence of stimulated radiation in MCT range of 2–2.5 μm at room temperature for optimized MCT structures grown on GaAs
substrates using the method of molecular beam epitaxy is shown experimentally. The obtained experimental data are the first
results of observation of stimulated radiation from the MCT structures at these wavelengths at room temperature. The gain
factor in the active medium measured for this case is very large and attains values of 50 cm−1, which allows one to hope that a further advance to a longer wavelengths is possible. 相似文献
3.
Band-edge photoluminescence spectra of heavily donor-doped samples of InxGa1−x
As1−y
Py (x=0.77, y=0.53) were investigated in the temperature range (77–300) K. A theory of luminescence that takes into account fluctuations
in the band-edge potentials due to nonuniform distribution of impurities is used to calculate temperature dependences of the
positions and half-widths of peaks in these spectra. Good agreement is obtained between experimental and calculated curves.
For heavily doped InxGa1−x
As1−y
Py samples with either p-or n-type conductivity, the peak energy of the band-edge PL is observed to shift towards lower frequencies at low temperatures.
This shift is accompanied by broadening of the spectra and a decrease in the photoluminescence intensity compared to the analogous
parameters for the spectra of undoped material. Possible mechanisms for radiative recombination are analyzed.
Fiz. Tekh. Poluprovodn. 33, 907–912 (August 1999) 相似文献
4.
A nonlocal empirical pseudopotential scheme that includes the spin-orbit interaction is used to calculate the electronic structure
of In1−x
GaxSb solid solutions. A modified virtualcrystal approximation is used to explain the nonlinear experimental dependence of the
width of the band gap on composition. The computed band structure is then used to calculate the dispersion of the dielectric
constant and compare it with experimental results.
Fiz. Tekh. Poluprovodn. 32, 1054–1056 (September 1998) 相似文献
5.
The reproducible molecular-beam epitaxy (MBE) growth of dual-band Hg1−xCdxTe (MCT) heterostructures requires routine post-growth wafer analysis for constituent layer thickness and alloy composition,
therefore, demanding nondestructive characterization techniques that offer quick data feedback. This paper reports a multilayer
structure model, which can be least-square fit directly to either Fourier transform infrared (FTIR) transmission or reflection
spectra to provide individual layer thickness, alloy composition, and grading information for various complex structures.
The model, we developed, is based on an accurate representation of both the real and imaginary parts of the MCT dielectric
function across and above E
g
as a function of alloy composition. The parametric, MCT optical-dielectric function for compositions varying between x=0.17
to x=0.5 was developed in the range from 400 cm−1 to 4,000 cm−1, based on a semi-empirical model for the absorption coefficient and extrapolation of the refractive index across E
g
. The model parameters were refined through simultaneous fits to multiple reflection and transmission data sets from as-grown,
double-layer planar heterostructure (DLPH) structures of variable thickness. The multilayer model was tested on a variety
of simple DLPH structures with thick absorber layers (>8 μm) and was compared against traditional FTIR analysis and cross-section
optical microscopy and showed good agreement in both composition and thickness. Model fits to dual-color MCT data and subsequent
analysis of the internal parameter correlation have demonstrated that error bars on absorber layer composition and thickness
could be as low as ∼0.0005 and ∼0.02 μm, correspondingly. 相似文献
6.
A procedure convenient for practical application to the calculations of the fundamental absorption spectra of semiconductor
alloys with the direct-gap energy-band structure is developed. The procedure is based on the knowledge of the fundamental
absorption spectra of binary constituents of the alloy, takes into account the nonparabolic structure of the conduction band,
and involves only one adjustable parameter that characterizes the inhomogeneous broadening of the spectra. The procedure is
tested by the examples of the best-studied and practically most important Al
x
Ga1 − x
As alloys, the (Al
x
Ga1 − x
)0.5In0.5P alloys isostructural to GaAs, and the Ga
x
In1 − x
As alloys isostructural to InP. The procedure can be used in the case of other III–V and II–VI compounds. The results make
it possible to calculate the intrinsic luminescence spectra of the alloys. 相似文献
7.
Electron spin resonance and the Hall effect are investigated in n-Pb1−x
SnxTe:Gd crystals grown from melt. It is found that there is no direct correlation between the free electron density and the
density of the Gd3+ impurity in these crystals. The conclusion is drawn that the the electron conductivity of Pb1−x
SnxTe:Gd crystals is not caused by the Gd impurity but by intrinsic defects of the crystal lattice which have zero activation
energy due to the Gd impurities.
Fiz. Tekh. Poluprovodn. 32, 1331–1333 (November 1998) 相似文献
8.
Dielectric ceramics based on the solid solution (1 − x)Bi0.5Na0.5TiO3 (BNT)-xCaTiO3 (CT) were synthesized by the conventional solid-state route. BNT with various contents of CT formed a complete solid solution
and exhibited a rhombohedral structure. CT in this solid solution with BNT was observed to decrease the dielectric constant
at higher temperatures and raise the dielectric constant at lower temperatures. On the other hand, decreased ferroelectricity
was observed with increasing CT concentration, resulting in a downward shift of the depolarization temperature and a decrease
of the dissipation factor. With the addition of Mn2+ to 0.86BNT-0.14CT, the temperature characteristics of capacitance were improved (−55°C to 250°C, ΔC/C
25°C ≤ ±15%). By doping with 1.5 wt.% Mn2+, the dielectric constant at room temperature reached over 900, with a dielectric loss of less than 1%. 相似文献
9.
R. Remya K. P. Murali S. N. Potty V. Priyadarshini R. Ratheesh 《Journal of Electronic Materials》2005,34(7):1076-1080
Hollandite-type Ba1−xSrxZnTi7O16 (x=0, 0.2, 0.4, 0.6, 0.8, and 1) ceramics have been synthesized by the conventional solid-state ceramic route. The phase
purity and microstructure of these compositions have been characterized using x-ray diffraction (XRD) and scanning electron
microscopy (SEM). The XRD analysis shows that an increase in strontium concentration in the A-site causes pairing of vacant
tunnel sites, and hence the structure becomes unstable due to the collapse of the tunnel walls. The dielectric properties
such as dielectric constant (εr), loss tangent (tan δ), and temperature variation of dielectric constant (τεr) have been measured up to the 13 MHz region. The present study shows that zinc hollandites have relatively high dielectric
constant and low loss tangent. The temperature variation of dielectric constant studies reveal that Ba-rich compositions have
high positive τεr and Sr-rich compositions have high negative τεr in the 0–100°C region. Proper tailor making of these compositions has been attempted to arrive at near-zero temperature variation
of the dielectric constant. 相似文献
10.
The luminescence spectra of blue and green light-emitting diodes based on InxGa1−x
N/AlyGa1−y
N/GaN heterostructures with a thin (2–3 nm) InxGa1−x
N active layer have been investigated in the temperature and current intervals 100–300 K and J=0.01–20 mA, respectively. The spectra of the blue and green light-emitting diodes have maxima in the interavals ℏωmax=2.55–2.75 eV and ℏωmax=2.38–2.50 eV, respectively, depending on the In content in the active layer. The spectral intensity of the principal band
decreases exponentially in the long-wavelength region with energy constant E
0=45–70 meV; this is described by a model that takes into account the tails of the density of states in the two-dimensional
active region and the degree of filling of the tails near the band edges. At low currents radiative tunneling recombination
with a voltage-dependent maximum in the spectrum is observed in the spectra of the blue diodes. A model of the energy diagram
of the heterostructures is discussed.
Fiz. Tekh. Poluprovodn. 31, 1055–1061 (September 1997) 相似文献
11.
Rare-earth-modified ferroelectric crystals with the formula (Sr1−xBax)1− 3y/2 RyNb22O6, where R = La, Nd, Sm, Gd, and Lu, have Been prepared and studied. When R = La, Nd, x ≃ .5 and y = 0.02, the modified material,
at room temperature, exhibited twice the pyroelectric coefficient and four times the dielectric constant of the unmodified
Sr1−xBaxNb2O6 (x ≃ .5). Curie temperatures decreased, dielectric constants increased, while loss factor and detector signal-to-noise ratios
remained nearly the same with the addition of rare earth doping. The calculated response based on the measured properties
agree with the measured response of actual detectors. These properties suggested that the modified SBN are good materials
for small element or array pyroelectric infrared detector applications. 相似文献
12.
R. S. Sillmon S. M. Hues D. K. Gaskill N. Bottka P. E. Thompson 《Journal of Electronic Materials》1989,18(4):501-504
We report on the OMVPE growth of modulation doped p-type Al0.43Ga0.57As(Be)/GaAs heterojunctions which exhibit a two-dimensional hole gas (2DHG). Hole mobilities de-termined by Hall or cyclotron
resonance measurements at 300, 77, and 4 K were 394, 3750, and 21200 cm2/V bs s respectively for a sheet carrier density of about 4.5 × 1011 cms−2. Beryllium doping of AlxGa1−xAs using diethylberyllium is characterized by Hall measurements, secondary ion mass spectrometry, and photoluminescence. The
depen-dence of free carrier concentrationvs AlAs% forp
+ layers of AlxGa1−xAsx,x = 0–0.5, is determined. A free carrier concentration greater than 1 × 1018 cms−3 is achieved forx = 0–0.43 with no carrier freeze-out down to 77 K. 相似文献
13.
E. C. Piquette M. Zandian D. D. Edwall J. M. Arias 《Journal of Electronic Materials》2001,30(6):627-631
A semi-empirical constraint to the thermodynamical model for growth of Hg1−xCdxTe (MCT) by molecular beam epitaxy is described. This constraint, derived by forcing the population of Hg atoms in a surface
layer to be proportional to the HgTe fractional growth rate, can determine an optimal total growth rate for specific beam
fluxes and substrate temperature. Utilizing improved growth conditions determined by this model has resulted in MCT layers
with consistently lower visible defect density (e.g., voids). The majority of recent layers grown using the constrained conditions
has achieved defect densities limited by the CdZnTe substrate. On the highest quality substrates, total defect densities have
consistently been reduced to the 100–200 cm−2 range using the improved conditions for compositions x=0.2 to x=0.6. On more typical substrates, the total defect density
is 1000–1500 cm−2. This compares with densities of 3000–5000+ cm−2 for old layers grown under non-optimized conditions. The density of voids has remained about the same upon using the improved
conditions, and is determined primarily by the Te precipitate content of the substrate, but microdefect (hillock) density
has been reduced by almost a factor of ten. 相似文献
14.
The scope of the present investigation is to make a clear contrast between the bandgap bowing characters of III–V and II–VI
compound-semiconductor common-cation ternary alloys. For this aim, both the sp
3
s
* tight-binding method, with the inclusion of spin–orbit coupling, and the full-potential linear augmented plane-wave technique
are used to calculate the partial and total densities of states, the constituent ionicity, and the total electron charge density
for the common-cation GaSb
x
As1−x
and CdSe
x
Te1−x
ternary alloys. The results show that the bowing is sensitive to competition between the anions for trapping/losing electric
charges. The lack of this competition would result in complete absence of the bowing, as is the case for common-anion ternary
alloys. In the common-cation ternary alloys studied herein, the bowing is found to be proportional to the electronegativity
of the anions χ
anion (i.e., the 6-valency anions are more electronegative than the 5-valency ones, and consequently the former result in stronger
intercompetition and yield stronger bowing in the II–VI alloys) and also proportional to the relative mismatch in electronegativity
between the competing anions
(\Updeltacanion/canionave).({\Updelta}\chi^{\rm{anion}}/\chi^{\rm{anion}}_{\rm{ave}}). The excellent agreement between our theoretical results and recent photoluminescence data corroborates our claim. 相似文献
15.
In this report,the diffusion of Zn,Zn-Cd in In_xGa_(1-x)As is investigated using ZnAs_2 and ZnAs_2+Cd as diffusion sources. The effect of the diffusion temperature,diffusion time,a variety of the diffusion source and composition x of the material on the relation of the(X_j-t~(1/2))are given.The diffusion velocity X_j~2/t of Zn in In_xGa_(1-x)As is faster than that of Zn-Cd in In_xGa_(1-x)As,and at 500-600℃,the surface acceptor concentration is from 1×10~(19)to 2×10~(20)cm~(-3),which is higher than that of Zn in InP.Reduction of contact resistance by use of In_xGa_(1-x)As contact layer for 1.3μm LED can be expected. 相似文献
16.
M. Gogna E. Suarez P.-Y. Chan F. Al-Amoody S. Karmakar F. Jain 《Journal of Electronic Materials》2011,40(8):1769-1774
This paper presents fabrication and characterization of a quantum dot-based floating gate nonvolatile memory device with site-specific
self-assembly of germanium oxide-cladded germanium (GeO
x
-Ge) quantum dots on SiO2 and ZnS/ZnMgS/ZnS (II–VI lattice-matched high-κ dielectric) tunnel insulator material. These monodispersed and individually cladded quantum dots have the potential to store
charge uniformly in the floating gate and are well suited for nonvolatile memory applications. 相似文献
17.
Janusz Tobola Stanislaw Kaprzyk Hubert Scherrer 《Journal of Electronic Materials》2010,39(9):2064-2069
We present electronic structure calculations of ordered Mg2Si as well as disordered Mg2Si1−x
Sb
x
and Mg2−δ
Si1−x
Sb
x
systems, carried out by the Korringa–Kohn–Rostoker method with the coherent potential approximation (KKR-CPA). The computed
densities of states (DOS) clearly show that a vacancy on the Mg site behaves as a double hole donor. Such electronic structure
behavior together with n-type doping by antimony leads to electron–hole compensation. Consequently, the semiconductor–metal crossover expected in
Mg2Si1−x
Sb
x
due to the Fermi level shift into conduction states is not observed when important vacancy defects appear on the Mg site.
Conversely, the Fermi level remains inside the energy gap if the antimony concentration is twice the vacancy concentration.
The possible origin of vacancy formation in Mg2Si1−x
Sb
x
is discussed based on the formation energy calculations as well as DOS features. Our KKR-CPA results well support recent
electron transport properties measurements. 相似文献
18.
A. I. Belogorokhov V. A. Kul’bachinskii P. D. Mar’yanchuk I. A. Churilov 《Semiconductors》1998,32(5):488-490
Reflection spectra of single crystals of Hg1−x
MnxTe1−y
Sey (0.01<x<0.14, y=0.01) in the far-infrared range (10–600 cm−1) are investigated at 300 and 77 K. A series of new phonon modes is observed, in addition to the longitudinal and transverse
modes corresponding to the ternary compounds.
Fiz. Tekh. Poluprovodn. 32, 546–548 (May 1998) 相似文献
19.
The effect of successive double implantation of Ag+(Cu+) and Xe+ ions on the recombination properties of CdxHg1−x
Te (0.2<x<0.3) crystals has been investigated. It is shown that after implantation of ions of one chemical element, followed by diffusion
thermal annealing at temperatures below 150–200 K, recombination through local levels lying 30±5 meV below the conduction
band bottom dominates. Successive double implantation of Ag+(Cu+) and Xe+ ions followed by diffusion thermal annealing changes the course of the temperature dependence of the lifetime of the nonequilibrium
charge carriers. It was determined that for CdxHg1−x
Te crystals with x⋍0.20–0.25 in the temperature interval 700–200 K the lifetime of the nonequilibrium charge carriers is low (τ<0.15 μs) and does not depend on the temperature. For CdxHg1−x
Te crystals with x⋍0.3 recombination of nonequilibrium charge carriers occurs through two types of levels: in the temperature range 140–200
K — deep levels E
t1⋍E
c
−51 meV and at lower temperatures (77–140 K) — through shallower levels E
t2⋍E
c
−(16±2) meV.
Fiz. Tekh. Poluprovodn. 31, 786–789 (July 1997) 相似文献
20.
This work deals with the study by means of radioactive tracers and autoradiography, as well as measuring of galvanomagnetic
properties, of Ga and In doping of epitaxial CdxHg1−xTe layers during their crystallization from a Te-rich melt. Ga and In were introduced in the form of Ga72 and In114 master alloys with Te. The effective distribution coefficients of Ga and In during the crystallization of the CdxHg1−xTe solid solutions with x=0.20 to 0.23 were determined by cooling the Te-base melt to 515–470°C. Depending on the concentration
of the dopants and the time-temperature conditions of CdxHg1−xTe growth, these ratios for Ga and In were 1.5–2.0 and 1.0–1.5, respectively. The electrical activity of Ga and In was determined
after annealing of the CdxHg1−xTe layers in saturated Hg vapor at 270–300°C. In doping of the epitaxial layers to (3–8)×1014 cm−3 with subsequent annealing in saturated Hg vapor at ∼270°C increases the carrier lifetime approximately by a factor of two
as compared with the undoped material annealed under the same conditions. 相似文献