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1.
The thermoelectric properties of PbTe/Te superlattice structures grown by molecular beam epitaxy have been investigated. The
in-plane Seebeck coefficient, Hall coefficient, and electrical resistivity have been measured at 300K. The data show that
a significant enhancement of the in-plane Seebeck coefficient, thermoelectric power factor and figure of merit has been achieved. 相似文献
2.
Hall-effect, conductivity and solubility measurements were carried out on Cd-diffused PbTe and Pb1−xSnxTe. Our results show that the Cd solubility in the crystals is independent of the tin mole fraction. The data, examined in
view of both Cd solubility and the influence of Cd upon the transport properties at 4.2K, indicate that after the metal vacancy
sites become fully compensated by the Cd atoms most of the Cd distributes uniformly as an electrically inactive impurity in
the crystal lattice. Saturation in electron concentration, which was observed at high Cd solubilities, provided a measure
of the excess ionized metal point-defect concentration generated in the crystals during the growth process. The product of
the concentrations of the excess metal and excess Te native point defects of the as-grown Pb1−xSnxTe was found to be practically constant for tin mole fractions 0≼x≼0.25, indicating that the equilibrium point defect constant
is independent of the tin content.
This work forms part of a thesis to be submitted by E. Silberg to the Weizmann Institute of Science in partial fulfillment
of the requirements for the Ph.D. degree. 相似文献
3.
Liquid-phase epitaxial (LPE) layers of Pb1−xSnxTe with an alloy composition 0≤×≤0.25 were doped n-type by adding from 0.002 to 10 at.% indium to the growth solution. Doping
characteristics of indium and electrical properties of the epilayers at 77 and 4.2K were studied by Hall and resistivity measurements
made directly on the grown layers. Electron concentration and mobility at 77 and 4.2K are presented as a function of indium
doping for various x values. Doping coefficients of ~0.05 and ~0.03 are found for PbTe and Pb0.8Sn0.2Te, respectively, grown at ~450°C. For medium to high indium doping, the electron concentration saturates to a constant value
independent of doping and LPE growth temperature. The saturation values decrease substantially with increasing x and increase
with a decrease in sample temperature. Bulklike mobilities practically independent of doping are recorded up to an indium
concentration Nln~0.3 at.%, above which the mobility decreases with increasing indium concentration. The data shows that indium is a suitable
donor in liquid-phase epitaxial layers of Pbl-XSnxTe. 相似文献
4.
C. R. Becker V. Latussek M. Li A. Pfeuffer-Jeschke G. Landwehr 《Journal of Electronic Materials》1999,28(6):826-829
The valence band offset (Λ) between HgTe and CdTe has been determined by means of an optical investigation of (112)B oriented
HgTe/Hg1−xCdxTe superlattices. Based on the fact that the difference in energy between the first heavy hole and the first light hole subband
is to a good approximation due primarily to Λ, it has been shown that Λ=580±40 meV at 5K. In addition Λ has a significant
temperature dependence with a linear coefficient of −0.34±0.02 meV/K, i.e., Λ is 480±40 meV at room temperature. 相似文献
5.
A. I. D’Souza M. G. Stapelbroek P. N. Dolan P. S. Wijewarnasuriya R. E. DeWames D. S. Smith J. C. Ehlert 《Journal of Electronic Materials》2003,32(7):633-638
The 1/f noise in photovoltaic (PV) molecular-beam epitaxy (MBE)-grown Hg1−xCdxTe double-layer planar heterostructure (DLPH) large-area detectors is a critical noise component with the potential to limit
sensitivity of the cross-track infrared sounder (CrIS) instrument. Therefore, an understanding of the origins and mechanisms
of noise currents in these PV detectors is of great importance. Excess low-frequency noise has been measured on a number of
1000-μm-diameter active-area detectors of varying “quality” (i.e., having a wide range of I-V characteristics at 78 K). The
1/f noise was measured as a function of cut-off wavelength under illuminated conditions. For short-wave infrared (SWIR) detectors
at 98 K, minimal 1/f noise was measured when the total current was dominated by diffusion with white noise spectral density
in the mid-10−15A/Hz1/2 range. For SWIR detectors dominated by other than diffusion current, the ratio, α, of the noise current in unit bandwidth
in(f = 1 Hz, Vd = −60 mV, and Δf = 1 Hz) to dark current Id(Vd = −60 mV) was αSW-d = in/Id ∼ 1 × 10−3. The SWIR detectors measured at 0 mV under illuminated conditions had median αSW-P = in/Iph ∼ 7 × 10−6. For mid-wave infrared (MWIR) detectors, αMW-d = in/Id ∼ 2 × 10−4, due to tunneling current contributions to the 1/f noise. Measurements on forty-nine 1000-μm-diameter MWIR detectors under
illuminated conditions at 98 K and −60 mV bias resulted in αMW-P = in/Iph = 4.16 ± 1.69 × 10−6. A significant point to note is that the photo-induced noise spectra are nearly identical at 0 mV and 100 mV reverse bias,
with a noise-current-to-photocurrent ratio, αMW-P, in the mid 10−6 range. For long-wave infrared (LWIR) detectors measured at 78 K, the ratio, αLW-d = in/Id ∼ 6 × 10−6, for the best performers. The majority of the LWIR detectors exhibited αLW-d on the order of 2 × 10−5. The photo-induced 1/f noise had αLW-P = in/Iph ∼ 5 × 10−6. The value of the noise-current-to-dark-current ratio, α appears to increase with increasing bandgap. It is not clear if
this is due to different current mechanisms impacting 1/f noise performance. Measurements on detectors of different bandgaps
are needed at temperatures where diffusion current is the dominant current. Excess low-frequency noise measurements made as
a function of detector reverse bias indicate 1/f noise may result primarily from the dominant current mechanism at each particular
bias. The 1/f noise was not a direct function of the applied bias. 相似文献
6.
The liquid-phase epitaxial growth of Pb1−xSnx Te on PbTe (100) substrates has been investigated over a range of growth temperatures from 600-400°C, and has been found
to produce material with good uniformity and reproducibility of carrier concen-tration and alloy composition. The assessment
of the epitaxial layers by such techniques as x-ray diffraction, dislocation etching and thermo-electric power measurements
is described. Various features of the epitaxial layers such as interface irregularity, dislocation and diffusion effects are
discussed, and likely mechanisms for their existence are proposed. The hole concentrations of the epitaxial layers, obtained
by thermoelectric power measurements, are shown to have a similar dependence on preparation temperature as for bulk annealed
material, suggesting that native defects are the dominant source of carriers above~ 2×10* cm-3. 相似文献
7.
The liquid-phase epitaxial growth of Pb1−xSnx Te on PbTe (100) substrates has been investigated over a range of growth temperatures from 600-400°C, and has been found
to produce material with good uniformity and reproducibility of carrier concen-tration and alloy composition. The assessment
of the epitaxial layers by such techniques as x-ray diffraction, dislocation etching and thermo-electric power measurements
is described. Various features of the epitaxial layers such as interface irregularity, dislocation and diffusion effects are
discussed, and likely mechanisms for their existence are proposed. The hole concentrations of the epitaxial layers, obtained
by thermoelectric power measurements, are shown to have a similar dependence on preparation temperature as for bulk annealed
material, suggesting that native defects are the dominant source of carriers above~ 2×10* cm-3.
The online version of the original article can be found at 相似文献
8.
In this paper we show that pseudomorphically strained heterostructures of InAs
x
P1−x
/InP may be an alternative to lattice-matched heterostructures of In1−x
Ga
x
As
y
P1−y
/InP for optoelectronic applications. We first studied the group-V composition control in the gas-source molecular beam epitaxy
(GSMBE) of the GaAs1-x
P
x
/GaAs system. Then we studied GSMBE of strained InAs
x
P1−x
/InP multiple quantum wells with the ternary well layer in the composition range 0.15 <x < 0.75. Structural and optical properties were characterized by high-resolution x-ray rocking curves, transmission electron
microscopy, absorption and low-temperature photoluminescence measurements. High-quality multiple-quantum-well structures were
obtained even for highly strained (up to 2.5%) samples. The achievement of sharp excitonic absorptions at 1.06, 1.3 and 1.55μm at room temperature from InAs
x
P1−x
/InP quantum wells suggests the possibility of long-wavelength optoelectronic applications. 相似文献
9.
F. C. Peiris M. R. Buckley O. Maksimov M. Munoz M. C. Tamargo 《Journal of Electronic Materials》2003,32(7):742-746
We have used a combination of prism-coupling, reflectivity, and ellipsometric techniques to investigate the indices of refraction,
n, of a series of BexZn1−xTe thin films grown on InP substrates. After determining the concentrations of each of the BexZn1−xTe alloys using x-ray diffraction measurements, we measured their n at discrete wavelengths using a prism-coupler setup. In
addition, we used reflectivity measurements to complement the prism-coupler data and arrive at the dispersion relations of
n for the BexZn1−xTe alloys below their fundamental energy gaps. We then employed a rotating analyzer-spectroscopic ellipsometer to measure
the complex reflection ratio for each of the films at angles of incidence of 65°, 70°, and 75°. By using the n values obtained
from both the prism-coupler and the reflection-spectroscopy techniques to guide the ellipsometric analysis, we were able to
obtain accurate results for the dispersion of n for the BexZn1−xTe alloys, not only below their fundamental energy gaps, but also above their energy gaps (up to 6.5 eV) using these three
complementary techniques. 相似文献
10.
Sridhar Govindaraju Jason M. Reifsnider Michael M. Oye Archie L. HolmesJr. 《Journal of Electronic Materials》2004,33(8):851-860
This article describes the effects of rapid thermal annealing (RTA) on the photoluminescence (PL) emission from a series of GaIn(N)As quantum wells. Indium compositions of both 20% and 32% were examined with nominal N compositions of 1% or 2%. The N location was varied within our quantum structure, which can be divided into three regions: (1) quantum well, (2) Ga(N)As spacer layers at the barrier-to-well interface and well-to-barrier interface, and (3) barriers surrounding each quantum well. Eight combinations of samples were examined with varying In content, Ga(N)As spacer layer thickness, N content, and N location in the structure. In the best cases, the presence of these Ga(N)As spacer layers improves the PL properties, due to annealing, with a reduction in the emission wavelength blueshift by ~400 Å, a reduction of the decrease in the full-width at half-maximum (FWHM) by ~5 meV, and a threefold reduction of the increase in integrated intensity. It was also observed that relocating N from the quantum wells to the barriers produces a comparable emission wavelength both before and after annealing. Our results further show that the composition of incorporated N in the material is most influential during the stages of RTA in which relatively small amounts of thermal energy is present from our lower annealing times and temperatures. Hence, we believe a low thermal-energy anneal is responsible for the recovery of the plasma-related crystal damage that was incurred during its growth. However, the In composition in the quantum well is most influential during the latter stages of thermal annealing, at increased times and temperatures, where the wavelength blueshift was roughly independent of the amount of incorporated N. As a result, our investigations into the effects of RTA on the PL properties support other reports that suggest the wavelength blueshift is not due to N diffusion. 相似文献
11.
Hg1−xCdxTe films were grown by a modified meltetch liquid phase epitaxial (LPE) technique which includes both substrate and epilayer
etchback steps. The crystal quality of epilayer has been investigated by means of transmission electron microscopy, scanning
electron microscopy, and double crystal x-ray diffraction. It has been found that adequate meltetch of the substrate at the
beginning of LPE provides a fresh and flat surface for epitaxial growth, while epilayer meltetch at the end of LPE may prevent
spurious melt sticking. 相似文献
12.
A novel set-up for horizontal open-tube vapor transport epitaxy of Hg1−xCdxTe films is described. Mirror-like Hg1−xCdxTe epitaxial layers with thicknesses up to 40 Μm were grown and characterized. The growth temperature ranged from 380 to 550‡C,
with growth rates of the order of 0.5–7 Μm per hour. The concentration depth profiles and the optical and electrical properties
of relatively uniform films with x≈0.3–0.4 are reported. The process kinetics are studied. A simple model which takes into
account the reactions occurring at the boundaries of the epitaxial layer and the interdiffusion in the epilayer is presented
and discussed. The model fits the experimentally observed characteristics of the epitaxial growth process. A constant growth
rate leading to a linear dependence of film thickness upon deposition time y–yi=ks t is derived. The reaction rate constant k is given by ks=koe−Ea/kT with ko=0.18 cm-sec−1and the energy of activation Ea=1.12 eV. 相似文献
13.
T. C. Harman 《Journal of Electronic Materials》1980,9(6):945-961
Liquidus isotherms for the Hg1−xCdxTe primary phase field in the Te-rich corner of the Hg-Cd-Te ternary system have been determined for temperatures from 425
to 600‡C by a modified direct observational technique. These isotherms were used to help establish conditions for the open-tube
liquid phase epitaxial growth of Hg1−xCdxTe layers on CdTe1−ySey substrates. Layers with x ranging from 0.1 to 0.8 have been grown from Te-rich HgCdTe solutions under flowing H2 by means of a horizontal slider technique that prevents loss of Hg from the solutions by evaporation. Growth temperatures
and times of 450–550‡C and 0.25–10 min, respectively, have been used. The growth solution equilibration time is typically
1 h at 550‡C. Source wafers, supercooled solutions, and (111)-oriented substrates were employed in growing the highest quality
layers, which were between 3 and 15 Μm thick. Electron microprobe analysis was used to determine x for the epitaxial layers,
and the resulting data, along with the liquidus isotherms, were used to obtain solidus lines. In addition to EMP data, optical
transmission results are given.
This work was sponsored by the Department of the Air Force and the U. S. Army Research Office. 相似文献
14.
Sidney G. Parker 《Journal of Electronic Materials》1976,5(5):497-511
The quality of PbxSn1−xTe crystals to be used in infrared detectors was improved by elimination or reduction in the number of holes, linear voids,
strains and dislocations during growth. This was accomplished by use of stoichiometric or slightly Te-rich charges preheat
treated before use to reduce the number of holes. Linear voids and strains were reduced by using constant diameter growth
tubes of 25 mm diameter. The number of dislocations was reduced by the use of a slow cooling rate and limited contract with
the walls of the growth tube. 相似文献
15.
J. R. Meyer K. A. Harris R. W. Yanka L. M. Mohnkern A. R. Reisinger J. F. Egler K. Mahalingam N. Otsuka 《Journal of Electronic Materials》1995,24(5):707-712
Infrared photoluminescence (PL) measurements were performed on (2ID-oriented superlattices with energy gaps in the range 110–495
meV. Most of the samples with thinner HgTe quantum wells displayed two PL peaks separated by Δhω ≈ 30–65 meV (which generally
increased with decreasing well thickness). Both peak energies (Ep) sometimes varied gradually with location on the surface, and in one case three peaks of approximately equal spacing were
observed in some locations. The data are consistent with a model which assumes the presence of randomly distributed islands
having well thicknesses varying by approximately one monolayer. We find that Ahco and the variations of the spectra with temperature
agree well with calculations based on this simple model. 相似文献
16.
As part of a systematic investigation of the effects of substrate surfaces on epitaxial growth, the transient behavior of
Hg1−xCdxTe film growth on (111)B CdTe by chemical vapor transport (CVT) has been studied as a function of growth time under vertical
stabilizing (hot end on top) and vertical destabilizing (hot end at bottom) ampoule orientations. The experim ental results
show the morphological transition of the Hg1−xCdxTe deposition on (111)B CdTe at 545°C from three-dimensional islands to layers within about 0.5 and 0.75 h for the growth
under vertical stabilizing and destabilizing conditions, respectively. The combined effects of small convective flow disturbances
on the growth morphology and defect formation are measurable. The overall trends of the time dependent growth rates and compositions
of the Hg1−xCdxTe epitaxial layers under stabilizing and destabilizing conditions are similar. The system atically higher growth rates of
the Hg1−xCdxTe films by about 10% under vertical destabilizing conditions could be influenced by a small convective contribution to the
mass transport. The combined results show that improved Hg1−xCdxTe epitaxial layers of low twin density on (111)B CdTe substrates can be obtained by CVT under vertical stabilizing conditions. 相似文献
17.
D. K. Sengupta S. L. Jackson A. P. Curtis W. Fang J. I. Malin T. U. Horton H. C. Kuo A. Moy J. Miller K. C. Hsieh K. Y. Cheng H. Chen I. Adesida S. L. Chuang M. Feng G. E. Stillman W. Wu J. Tucker Y. C. Chang L. Li H. C. Liu 《Journal of Electronic Materials》1997,26(12):1382-1388
High-quality InGaAs/InP quantum wells with ultra-narrow well widths (∼10?) and peak response at 4.55 μm were grown by gas
source molecular beam epitaxy. These structures were characterized by cross-sectional tunneling microscopy (XSTM), double-crystal
x-ray diffraction (DCXRD), and cross-sectional transmission electron microscopy (XTEM). Based on the structural parameters
determined by XTEM, XSTM, and DCXRD, the field dependent photocurrent spectra were simulated using a six-band effective bond-orbital
model. The theoretical calculations are in excellent agreement with experimental data. When used to fabricate p-type InGaAs/InP
quantum-well infrared photodetectors (QWIPs), and combined with the high responsivity of 8.93 μm n-type InGaAs/InP QWIPs,
these structures offer the possibility of dual band monolithically integrated QWIPs. 相似文献
18.
Ultra-high vacuum chemical vapor deposition is particularly suitable for growth of band gap engineered GexSi1?x structures, since abrupt epilayers with a very high degree of uniformity can be obtained. We have grown multi-quantum well structures over a range of well widths and have characterized them by photoluminescence spectroscopy. We have observed prominent quantum well-related features that shift to higher energy in samples with narrower well widths. Spectra taken from various points on a 75 mm wafer show a maximum variation of ±3 meV in position of the no phonon peak in the 35Å well multi-quantum well sample. 相似文献
19.
Wayne Lo 《Journal of Electronic Materials》1977,6(1):39-48
Single crystals of Pb1−x Snx Te (0.06<x<0.08) have been grown by using an ingot-nucleation technique from a Te-rich source. The as-grown crystals have
a p-type carrier concentration around 1019 cm−3 and dislocation density as low as 103 cm−2. Diode lasers fabricated from these crystals have contact resistances of 2×10−5 Ω-cm2 and a single-mode single-ended output power of 750 μW at heat sink temperatures around 15 K. 相似文献
20.
By using a prism coupler technique in conjunction with reflectivity measurements, we have obtained highly accurate relations
for the dispersion of the indices of refraction n for a series of MBE-grown Cd1−xZnxTe alloys. Initially, the prism coupler technique was used to determine n at discrete wavelengths with an accuracy of at least
0.1%, and also to concurrently determine the epilayer thicknesses with an uncertainty of less than 0.5%. Having obtained precise
values for both n (at discrete wavelengths) and the thicknesses of the Cd1−xZnxTe epilayers, we were then able to correctly decipher the values for n at the maxima and minima of the reflectivity spectra
observed on the above epilayers, and thereby generate a continuous variation of the indices of refraction as a function of
wavelength. Fitting the dispersion of n in each alloy to a Sellmeier-type dispersion relation, we have obtained the dependence
of the constants appearing in this relation on the alloy concentration. This enables one to predict n not only as a function
of wavelength, but also as a function of alloy composition. 相似文献