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1.
Microstructural and optical characterization of CdTe(211)B/ZnTe/Si(211) grown by molecular beam epitaxy 总被引:2,自引:0,他引:2
S. Rujirawat David J. Smith J. P. Faurie G. Neu V. Nathan S. Sivananthan 《Journal of Electronic Materials》1998,27(9):1047-1052
CdTe layers have been grown by molecular beam epitaxy on 3 inch nominal Si(211) under various conditions to study the effect
of growth parameters on the structural quality. The microstructure of several samples was investigated by high resolution
transmission electron microscopy (HRTEM). The orientation of the CdTe layers was affected strongly by the ZnTe buffer deposition
temperature. Both single domain CdTe(133)B and CdTe(211)B were obtained by selective growth of ZnTe buffer layers at different
temperatures. We demonstrated that thin ZnTe buffer layers (<2 nm) are sufficient to maintain the (211) orientation. CdTe
deposited at ∼300°C grows with its normal lattice parameter from the onset of growth, demonstrating the effective strain accommodation
of the buffer layer. The low tilt angle (<1°) between CdTe[211] and Si[211] indicates that high miscut Si(211) substrates
are unnecessary. From low temperature photoluminescence, it is shown that Cd-substituted Li is the main residual impurity
in the CdTe layer. In addition, deep emission bands are attributed to the presence of AsTe and AgCd acceptors. There is no evidence that copper plays a role in the impurity contamination of the samples. 相似文献
2.
S. R. Rao S. S. Shintri J. K. Markunas R. N. Jacobs I. B. Bhat 《Journal of Electronic Materials》2011,40(8):1790-1794
High-quality (211)B CdTe buffer layers are required during Hg1−x
Cd
x
Te heteroepitaxy on Si substrates. In this study, direct metalorganic vapor-phase epitaxy (MOVPE) of (211)B CdTe on Si, as
well as CdTe on Si using intermediate Ge and ZnTe layers, has been achieved. Tertiary butyl arsine was used as a precursor
to enable As surfactant action during CdTe MOVPE on Si. The grown CdTe/Si films display a best x-ray diffraction rocking-curve
full-width at half-maximum of 64 arc-s and a best Everson etch pit density of 3 × 105 cm−2. These values are the best reported for MOVPE-grown (211)B CdTe/Si and match state-of-the-art material grown using molecular-beam
epitaxy. 相似文献
3.
S. R. Rao S. S. Shintri J. K. Markunas R. N. Jacobs I. B. Bhat 《Journal of Electronic Materials》2010,39(7):996-1000
High-quality (211)B CdTe buffer layers on Si substrates are required to enable Hg1–x
Cd
x
Te growth and device fabrication on lattice-mismatched Si substrates. Metalorganic vapor-phase epitaxy (MOVPE) of (211)B CdTe
on Si substrates using Ge and ZnTe interlayers has been achieved. Cyclic annealing has been used during growth of thick CdTe
layers in order to improve crystal quality. The best (211)B CdTe/Si films grown in this study display a low x-ray diffraction
(XRD) rocking-curve full-width at half-maximum (FWHM) of 85 arcsec and etch pit density (EPD) of 2 × 106 cm−2. These values are the best reported for MOVPE-grown (211) CdTe/Si and are comparable to those for state-of-the-art molecular
beam epitaxy (MBE)-grown CdTe/Si. 相似文献
4.
报道了用MBE的方法,在3英寸Si衬底上制备ZnTe/CdTe(211)B复合衬底材料的初步研究结果,该研究结果将能够直接应用于大面积Si基HgCdTe IRFPA材料的生长.经过Si(211)衬底低温表面处理、ZnTe低温成核、高温退火、高温ZnTe、CdTe层的生长研究,用MBE方法成功地获得了3英寸Si基ZnTe/CdTe(211)B复合衬底材料.CdTe厚度大于10μm,XRD FWHM平均值为120arc sec,最好达到100arc sec,无(133)孪晶和其他多晶晶向. 相似文献
5.
通过理论计算获得ZnTe/Si(211)与ZnTe/GaAs(211)异质结构样品室温下的热应变分布与曲率半径,并采用激光干涉仪测量两个样品室温下的曲率半径。研究发现,在(211)面上进行异质外延,两个互相垂直的晶向方向[1-1-1]和[01-1]的应变分布呈现各向异性,且沿两个方向上的表面曲率半径亦存在差异。ZnTe/GaAs(211)样品的激光干涉测量结果与理论计算较为吻合,均为同一数量级的表面曲率半径方向为负的张应变,ZnTe/Si(211)样品的测量结果则存在较大差异。由于Si衬底在高温脱氧的过程中产生了表面曲率半径方向为正的塑性形变,在一定程度上降低了外延ZnTe后异质结构的弯曲程度,减小了热失配应变。 相似文献
6.
M. Jaime-Vasquez R.N. Jacobs C. Nozaki J.D. Benson L.A. Almeida J. Arias J. Pellegrino 《Journal of Electronic Materials》2012,41(10):2975-2980
We present the results of a detailed study of the changes that occur on CdTe buffer layer surfaces grown on ZnTe/Si(211) and GaAs(211)B during the routine thermal cyclic annealing (TCA) process. Observations indicate that CdTe buffer layer surfaces are Te saturated when the TCA is performed under Te overpressure. In the absence of Te flux during the TCA step, the CdTe surface loses CdTe congruently and the typical CdTe nanowires show the presence of nodules on their surfaces. The observed changes in reflection high-energy electron diffraction patterns during TCA are explained in terms of surface chemistry and topography observations. Overall, the Te overpressure is necessary to maintain a smoother and pristine surface to continue the molecular beam epitaxy (MBE) growth. 相似文献
7.
Y. P. Chen G. Brill E. M. Campo T. Hierl J. C. M. Hwang N. K. Dhar 《Journal of Electronic Materials》2004,33(6):498-502
We report on the first successful growth of the quaternary alloy Cd1−yZnySexTe1−x(211) on 3-in. Si(211) substrates using molecular beam epitaxy (MBE). The growth of CdZnSeTe was performed using a compound
CdTe effusion source, a compound ZnTe source, and an elemental Se effusion source. The alloy compositions (x and y) of the
Cd1−yZnySexTe1−x quaternary compound were controlled through the Se/CdTe and ZnTe/CdTe flux ratios, respectively. Our results indicated that
the surface morphology of CdZnSeTe improves as the Zn concentration decreases, which fits well with our previous observation
that the surface morphology of CdZnTe/Si is poorer than that of CdSeTe/Si. Although the x-ray full-width at half-maximums
(FWHMs) of CdZnSeTe/Si with 4% of Zn + Se remain relatively constant regardless of the individual Zn and Se concentrations,
etched-pit density (EPD) measurements exhibit a higher dislocation count on CdZnSeTe/Si layers with about 2% Zn and Se incorporated.
The enhancement of threading dislocations in these alloys might be due to an alloy disorder effect between ZnSe and CdTe phases.
Our results indicate that the CdZnSeTe/Si quaternary material with low Zn or low Se concentration (less than 1.5%) while maintaining
4% total Zn + Se concentration can be used as lattice-matching composite substrates for long-wavelength infrared (LWIR) HgCdTe
as an alternative for CdZnTe/Si or CdSeTe/Si. 相似文献
8.
We have achieved metalorganic vapor-phase epitaxial growth of (211)B CdTe on Si without the requirement of a pregrowth high-temperature
oxide desorption step. This was achieved by growing a thin Ge film on the starting (211) Si substrates. To get (211)B CdTe
orientation, the Ge surface was exposed to As prior to the start of CdTe growth. A thin ZnTe interlayer between Ge and CdTe
has been shown to improve the CdTe surface morphology. 相似文献
9.
Shashidhar Shintri Sunil Rao Priyalal Wijewarnasuriya Sudhir Trivedi Ishwara Bhat 《Journal of Electronic Materials》2012,41(10):2824-2827
We report on the investigation of epitaxial cadmium telluride grown by metalorganic vapor-phase epitaxy (MOVPE) on (211)Si, with particular emphasis on studying the effect of changing the reactor parameters and thermal annealing conditions on the epilayer quality. The CdTe films were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), and x-ray diffraction (XRD). The best CdTe films were observed when the Te/Cd precursor partial pressure ratio was close to 3.1. It was also observed that, though annealing improved the crystal quality, a slight increase in surface roughness was observed. Similar attempts were made to improve the growth conditions of ZnTe intermediate buffer layer, which showed similar trends with changes in precursor flows. 相似文献
10.
The growth of CdTe buffer layers on (211)B GaAs substrates by organometallic vapor phase epitaxy (OMVPE) was studied, and
it was found that, depending on the growth conditions, either the (211) or (133) epitaxial orientation could be formed. In
some cases, an epilayer showing a mixed (211) and (133) orientation was also observed. The influence of several growth parameters
on the orientation of the CdTe layer was investigated, and it was found that the Te/Cd ratio, together with the growth temperature,
have the most significant effect in determining the epilayer orientation. From these results, it was then possible to select
nominally optimized growth conditions for CdTe buffer layers of both orientations. (Hg,Cd)Te layers of the same orientations
could then be grown and characterized. Although double crystal x-ray diffraction measurements indicated a somewhat better
crystalline perfection in the (133) (Hg,Cd)Te layers, these layers showed a poor surface morphology compared to the (211)
orientation. Measurement of etch pit densities also indicated defect densities to be typically half an order of magnitude
higher in the (133) orientation. Diodes were formed by ion implantation in both orientations and significantly better results
were obtained on the (211) (Hg,Cd)Te layers. 相似文献
11.
Evaluation of Surface Cleaning of Si(211) for Molecular-Beam Epitaxy Deposition of Infrared Detectors 总被引:1,自引:0,他引:1
M. Jaime-Vasquez R. N. Jacobs J. D. Benson A. J. Stoltz L. A. Almeida L. O. Bubulac Y. Chen G. Brill 《Journal of Electronic Materials》2010,39(7):951-957
We report an assessment of the reproducibility of the HF cleaning process and As passivation prior to the nucleation of ZnTe
on the Si(211) surface using temperature desorption spectroscopy, ion scattering spectroscopy, and electron spectroscopy.
Observations suggest full H coverage of the Si(211) surface with mostly monohydride and small amounts of dihydride states,
and that F is uniformly distributed across the top layer as a physisorbed species. Variations in major contaminants are observed
across the Si surface and at the CdTe-ZnTe/Si interface. Defects act as getters for impurities present on the Si surface,
and some are buried under the CdTe/ZnTe heterostructure. Overall, the data show evidence of localized concentration of major
impurities around defects, supporting the hypothesis of a physical model explaining the electrical activation of defects in
long-wave infrared (LWIR) HgCdTe/CdTe/Si devices. 相似文献
12.
Giacomo Badano Patrice Gergaud Ivan C. Robin Xavier Baudry Benoît Amstatt Fréderique Gemain 《Journal of Electronic Materials》2010,39(7):908-911
We have used x-ray diffraction to assess the thickness dependence of strain in molecular-beam epitaxial (MBE) CdTe(211)/Ge(211).
For 25-nm-thick layers, we find tensile stress of 100 MPa and in-plane strain of ~1.5 × 10−3. This stress relaxes during growth and becomes zero beyond 1 μm. We use the Dunn and Koch formula to estimate the threading dislocation density from the full-width at half-maximum of the
(224) rocking curve. We then estimate the annihilation radius of MBE-grown CdTe(211)B/Ge(211) to be ~10 nm. Our layers have
etch pit densities between 5 × 107 cm−2 and 5 × 106 cm−2 for a thickness of 10 μm. The lowest densities were obtained by periodic annealing epitaxy. We discuss mechanisms for the saturation of the dislocation
density. 相似文献
13.
Determination of Critical Thickness for Epitaxial ZnTe Layers Grown by Molecular Beam Epitaxy on (211)B and (100) GaSb Substrates 总被引:1,自引:0,他引:1
J. Chai O. C. Noriega A. Dedigama J. J. Kim A. A. Savage K. Doyle C. Smith N. Chau J. Pena J. H. Dinan D. J. Smith T. H. Myers 《Journal of Electronic Materials》2013,42(11):3090-3096
Cross-section electron micrographs, cathodoluminescence images, and confocal photoluminescence (cPL) images have been acquired for ZnTe layers deposited to various thicknesses on GaSb substrates with (211)B and (100) orientations. The critical thickness of ZnTe on GaSb is predicted to range between 115 nm and 329 nm, depending on the theoretical approach chosen. For ZnTe layers grown on (211)B GaSb with thickness exceeding 150 nm, dark spots and lines are present in all images. We associate these with dislocations generated at the ZnTe/GaSb interface. The discrepancy between this thickness value and a critical thickness value (350 nm to 375 nm) obtained for the (211)B orientation in a previous study is related to the distinction between the onset of misfit dislocations and the onset of significant plastic deformation. The former requires a direct imaging technique, as strain-related measurements such as x-ray diffraction do not have the resolution to detect the effects of small numbers of dislocations. For ZnTe layers on (100) GaSb, x-ray diffraction measurements indicate an abrupt change characteristic of dislocation multiplication at a thickness value in the range from 250 nm to 275 nm. High-resolution electron micrographs of the ZnTe/GaSb interface indicate that deoxidation using atomic hydrogen produces GaSb surfaces suitable for ZnTe epitaxy. cPL images of a 1.2-μm-thick lattice-matched ZnTe0.99Se 0.01 layer grown on a 150-nm-thick ZnTe buffer layer on a (211)B GaSb substrate yield a threading dislocation density of ~7 × 104 cm?2. 相似文献
14.
S. Fahey R. Bommena R. Kodama R. Sporken S. Sivananthan 《Journal of Electronic Materials》2012,41(10):2899-2907
We report here the use of molecular beam epitaxy (MBE) to achieve selective-area epitaxy (SAE) and coalescence of CdTe on nanopatterned substrates with 0.5-μm-pitch arrays of CdTe/ZnTe/Si(211) seeding areas, exposed through a silicon nitride mask. The nanopatterned substrate surface morphology, crystallinity, and chemical composition were characterized by scanning electron microscopy (SEM), x-ray diffraction (XRD), and x-ray photoelectron spectroscopy (XPS) both before and after exposure to CdTe flux by MBE. We find a seven times wider (422) CdTe XRD rocking curve full-width at half-maximum (FWHM) for our patterned samples, when directly compared with unpatterned samples with identical growth and pregrowth conditions. We also observe that electron beam-induced carbon deposits can serve as a mask material for SAE of CdTe by MBE. Finally, we point to possible further improvements in patterned sample architectures of the future, for use in CdTe films on Si. 相似文献
15.
Epitaxial (100) CdTe and ZnTe layers with high crystalline quality have been grown on Si substrates by atmospheric pressure
organometallic vapor phase epitaxy (OMVPE). A thin Ge interfacial layer grown at low temperature was used as a buffer layer
prior to ZnTe and CdTe growth. The layers were characterized by Nomarski optical microscopy and double crystal x-ray diffraction.
Double crystal rocking curves with full width at half maximum of about 110 and 250 arc-sec have been obtained for a 7 μm thick
ZnTe layer and a 4 μm thick CdTe layer, respectively. The results presented demonstrate a novel method ofin-situ Si cleaning step without a high temperature deoxidation process to grow high quality CdTe and ZnTe on Si in a single OMVPE
reactor. 相似文献
16.
M. Niraula K. Yasuda H. Ohnishi H. Takahashi K. Eguchi K. Noda Y. Agata 《Journal of Electronic Materials》2006,35(6):1257-1261
Direct growth of high-quality, thick CdTe (211) epilayers, with thickness up to 100 μm, on Si (211) substrates in a vertical
metalorganic vapor phase epitaxy system is reported. In order to obtain homo-orientation growth on Si substrates, pretreatment
of the substrates was carried out in a separate chamber by annealing them together with pieces of GaAs at 800–900°C in a hydrogen
environment. Grown epilayers had very good substrate adhesion. The full-width at half-maximum (FWHM) value of the x-ray double-crystal
rocking curve from the CdTe (422) reflection decreased rapidly with increasing layer thickness and remained between 140–200
arcsec for layers >18 μm. Photoluminescence measurement at 4.2 K showed high-intensity, bound excitonic emission and very
small defect-related deep emissions, indicating the high crystalline quality of the grown layers. Furthermore, a CdTe/n+-Si heterojunction diode was fabricated that exhibited clear rectifying behavior. 相似文献
17.
18.
X.J. Wang C. Fulk F.H. Zhao D.H. Li S. Mukherjee Y. Chang R. Sporken R. Klie Z. Shi C.H. Grein S. Sivananthan 《Journal of Electronic Materials》2008,37(9):1200-1204
Narrow-bandgap PbSnSe has received much attention as a promising alternative material for mid- and long-wavelength high performance
of infrared detection at relatively high operating temperatures owing to the weak composition dependence of its bandgap, which
can intrinsically result in better uniformity. Additionally, it possesses a high dielectric constant that is anticipated to
be much more tolerant to defects. In addition, its growth by molecular beam epitaxy (MBE) can be easily accomplished in comparison
with HgCdTe and many III–V quantum well and superlattice materials. However, overcoming the high lattice and thermal mismatches
between PbSnSe and CdTe/Si substrates and improving the crystalline quality of PbSnSe grown on CdTe/Si substrates are challenges
that require further study. Additionally, interdiffusion between CdTe and PbSnSe can take place and lead to nonuniform distributions
of elements in PbSnSe. Epitaxial crystal PbSnSe alloy films were grown by MBE and were investigated by scanning and high-resolution
transmission electron microscopy (STEM/HRTEM). Etch pit density (EPD) measurements were done to determine the density of threading
defects in the films. EPD measurements on PbSnSe surfaces gave values in the mid-106 cm−2 range. The dislocations exposed as etch pits were found to accumulate and form small-angle grain boundaries lined up along
the () direction, which is the intersection line between (100) and (211) growth planes. 相似文献
19.
The adsorption of CdTe layers on clean and As-passivated Si(211) substrates has been simulated by first-principle calculations
in this study. Based on the simulation results, we theoretically show the important roles of the As4 passivation during the epitaxial growth. Arsenic can saturate part of the dangling bonds and weaken the surface states. The
partial passivation finally induces the B-face polarity selection automatically. This conclusion can provide further explanations
for the successful growth of large area high-quality CdTe(211)B layers on the Si(211) substrates. 相似文献
20.
J. D. Benson L. O. Bubulac C. M. Lennon R. N. Jacobs P. J. Smith J. K. Markunas M. Jaime-Vasquez L. A. Almeida A. Stoltz J. A. Arias G. Brill Y. Chen P. S. Wijewarnasuriya M. F. Vilela J. Peterson S. M. Johnson D. D. Lofgreen D. Rhiger E. A. Patten J. Bangs 《Journal of Electronic Materials》2013,42(11):3217-3223
The crystalline structure and impurity profiles of HgCdTe/CdTe/alternate substrate (AS; Si and GaAs are possibilities) and CdTe/AS were analyzed by secondary-ion mass spectrometry, atomic force microscopy, etch pit density analysis, and scanning transmission electron microscopy. Impurities (Li, Na, and K) were shown to getter in as-grown CdTe/Si epilayers at in situ Te-stabilized thermal anneal (~500°C) interfaces. In HgCdTe/CdTe/Si epilayers, indium accumulation was observed at Te-stabilized thermal anneal interfaces. Impurity accumulation was measured at HgCdTe/CdTe and CdTe/ZnTe interfaces. Processing anneals were found to nearly eliminate the gettering effect at the in situ Te-stabilized thermal anneal interfaces. Impurities were found to redistribute to the front HgCdTe/CdTe/Si surface and p–n junction interfaces during annealing steps. We also investigated altering the in situ Te-stabilized thermal anneal process to enhance the gettering effect. 相似文献