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1.
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
2.
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
3.
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
4.
J. Zhao Y. Chang G. Badano S. Sivananthan J. Markunas S. Lewis J. H. Dinan P. S. Wijewarnasuriya Y. Chen G. Brill N. Dhar 《Journal of Electronic Materials》2004,33(8):881-885
We present results on the surface morphology and recombination lifetimes of molecular-beam epitaxy (MBE)-grown HgCdTe (211)B
epilayers and correlate them with the roughness of the CdZnTe substrate surfaces. The substrate surface quality was monitored
by in-situ spectroscopic ellipsometry (SE) and reflection high-energy electron diffraction (RHEED). The SE roughness of the
substrate was measured after oxide desorption in the growth chamber. The RHEED patterns collected show a strong correlation
with the SE roughness. This proves that SE is a valuable CdZnTe prescreening tool. We also found a correlation between the
substrate roughness and the epilayer morphologies. They are characterized by a high density of thin elongated defects, “needle
defects,” which appear on most samples regardless of growth conditions. The HgCdTe epilayers grown on these substrates were
characterized by temperature-dependent, photoconductive decay-lifetime data. Fits to the data indicate the presence of mid-gap
recombination centers, which were not removed by 250°C/24-h annealing under a Hg-rich atmosphere. These centers are believed
to originate from bulk defects rather than Hg vacancies. We show that Te annealing and CdTe growth on the CdZnTe substrates
smooth the surface and lower substantially the density of needle defects. Additionally, a variety of interfacial layers were
also introduced to reduce the defect density and improve the overall quality of the epilayer, even in the presence of less
than perfect substrates. Both the perfection of the substrate surface and that of its crystalline structure are essential
for the growth of high-quality material. Thus, CdZnTe surface polishing procedures and growth techniques are crucial issues. 相似文献
5.
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
6.
M. S. Han S. R. Hahn H. C. Kwon Y. Bin T. W. Kang J. H. Leem Y. B. Hou H. C. Jeon J. K. Hyun Y. T. Jeoung H. K. Kim J. M. Kim T. W. Kim 《Journal of Electronic Materials》1998,27(6):680-683
Double-crystal x-ray rocking curve (DCRC) and secondary-ion mass-spectroscopy (SIMS) measurements have been performed to investigate the effect of rapid thermal annealing on the interdiffusion behavior of Hg in HgTe/CdTe superlattices grown on Cd0.96Zn0.04Te (211)B substrates by molecular beam epitaxy. The sharp satellite peaks of the DCRC measurements on a 100-period HgTe/CdTe (100Å/100Å) superlattice show a periodic arrangement of the superlattice with high-quality interfaces. The negative direction of the entropy change obtained from the diffusion coefficients as a function of the reciprocal of the temperature after RTA indicates that the Hg diffusion for the annealed HgTe/CdTe superlattice is caused by an interstitial mechanism. The Cd and the Hg concentration profiles near the annealed HgTe/CdTe superlattice interfaces, as measured by SIMS, show a nonlinear behavior for Hg, originating from the interstitial diffusion mechanism of the Hg composition. These results indicate that a nonlinear interdiffusion behavior is dominant for HgTe/CdTe superlattices annealed at 190°C and that the rectangular shape of HgTe/CdTe superlattices may change to a parabolic shape because of the intermixing of Hg and Cd due to the thermal treatment. 相似文献
7.
Heteroepitaxy of HgCdTe (211)B on Ge substrates by molecular beam epitaxy for infrared detectors 总被引:3,自引:0,他引:3
J. P. Zanatta P. Ferret G. Theret A. Million M. Wolny J. P. Chamonal G. Destefanis 《Journal of Electronic Materials》1998,27(6):542-545
Epitaxial growth of (211)B CdTe/HgCdTe has been achieved on two inch germanium (Ge) by molecular beam epitaxy (MBE). Germanium
was chosen as an alternative substrate to circumvent the weaknesses of CdZnTe wafers. The ease of surface preparation makes
Ge an attractive candidate among many other alternative substrates. Best MBE CdTe growth results were obtained on (211) Ge
surfaces which were exposed to arsenic and zinc fluxes prior to the MBE growth. This surface preparation enabled CdTe growth
with B-face crystallographic polarity necessary for the HgCdTe growth. This process was reproducible, and produced a smooth
and mirror-like surface morphology. The best value of the {422} x-ray double diffraction full width at half maximum measured
from the HgCdTe layer was 68 arc-s. We present the 486 point maps of FWHM statistical values obtained from CdTe/Ge and HgCdTe/CdTe/Ge.
High resolution microscopy electron transmission and secondary ion mass spectroscopy characterization results are also presented
in this paper. High-performance middle wavelength infrared HgCdTe 32-element photodiode linear arrays, using the standard
LETI/LIR planar n-on-p ion implanted technology, were fabricated on CdTe/Ge substrates. At 78K, photodiodes exhibited very
high R0A figure of merit higher than 106 Ωcm−2 for a cutoff wavelength of 4.8 μm. Excess low frequency noise was not observed below 150K. 相似文献
8.
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
9.
M. Carmody A. Yulius D. Edwall D. Lee E. Piquette R. Jacobs D. Benson A. Stoltz J. Markunas A. Almeida J. Arias 《Journal of Electronic Materials》2012,41(10):2719-2724
Alternate substrates for molecular beam epitaxy growth of HgCdTe including Si, Ge, and GaAs have been under development for more than a decade. MBE growth of HgCdTe on GaAs substrates was pioneered by Teledyne Imaging Sensors (TIS) in the 1980s. However, recent improvements in the layer crystal quality including improvements in both the CdTe buffer layer and the HgCdTe layer growth have resulted in GaAs emerging as a strong candidate for replacement of bulk CdZnTe substrates for certain infrared imaging applications. In this paper the current state of the art in CdTe and HgCdTe MBE growth on (211)B GaAs and (211) Si at TIS is reviewed. Recent improvements in the CdTe buffer layer quality (double crystal rocking curve full-width at half-maximum?≈?30?arcsec) with HgCdTe dislocation densities of ≤106?cm?2 are discussed and comparisons are made with historical HgCdTe on bulk CdZnTe and alternate substrate data at TIS. Material properties including the HgCdTe majority carrier mobility and dislocation density are presented as a function of the CdTe buffer layer quality. 相似文献
10.
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
11.
J.D. Benson L.A. Almeida M.W. Carmody D.D. Edwall J.K. Markunas R.N. Jacobs M. Martinka U. Lee 《Journal of Electronic Materials》2007,36(8):949-957
The as-grown molecular beam epitaxy (MBE) (211)B HgCdTe surface has variable surface topography, which is primarily dependent on substrate temperature and substrate/epilayer mismatch. Nano-ripple formation and cross-hatch patterning are the predominant structural features observed. Nano-ripples preferentially form parallel to the \( [\bar {1}11] \) and are from 0 Å to 100 Å in height with a wavelength between 0.1 μm and 0.8 μm. Cross-hatch patterns result from slip dislocations in the three {111} planes intersecting the (211) growth surface. The cross-hatch step height is 4 ± 1 Å (limited data set). This indicates that only a bi-layer slip (Hg/Cd + Te) in the {111} slip plane occurs. For the deposition of MBE (211)B HgCdTe/CdTe/Si, the reorientation of multiple nano-ripples coalesced into “packets” forms cross-hatch patterns. The as-grown MBE (211)B CdTe/Si surface is highly variable but displays nano-ripples and no cross-hatch pattern. Three types of defects were observed by atomic force microscopy (AFM): needle, void/hillock, and voids. 相似文献
12.
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
13.
Jae Jin Kim R. N. Jacobs L. A. Almeida M. Jaime-Vasquez C. Nozaki David J. Smith 《Journal of Electronic Materials》2013,42(11):3142-3147
A microstructural study of HgCdTe/CdTe/GaAs(211)B and CdTe/GaAs(211)B heterostructures grown using molecular beam epitaxy (MBE) was carried out using transmission electron microscopy and small-probe microanalysis. High-quality MBE-grown CdTe on GaAs(211)B substrates was demonstrated to be a viable composite substrate platform for HgCdTe growth. In addition, analysis of interfacial misfit dislocations and residual strain showed that the CdTe/GaAs interface was fully relaxed except in localized regions where GaAs surface polishing had caused small pits. In the case of HgCdTe/CdTe/GaAs(211)B, the use of thin HgTe buffer layers between HgCdTe and CdTe for improving the HgCdTe crystal quality was also investigated. 相似文献
14.
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
15.
W. F. ZHAO R. N. JACOBS M. JAIME-VASQUEZ L. O. BUBULAC DAVID J. SMITH 《Journal of Electronic Materials》2011,40(8):1733-1737
Transmission electron microscopy and small-probe microanalysis have been used to investigate the microstructure and compositional
profiles of CdTe(211)B/ZnTe/Si(211) heterostructures. Thin ZnTe buffer layers and subsequent thick CdTe layers were grown
on Si(211) substrates using molecular beam epitaxy. Many {111}-type stacking faults were found to be present throughout the
entire ZnTe layer, terminating near the point of initiation of CdTe growth. A rotation angle of about 3.5° was observed between
lattice planes of the Si substrate and the final CdTe epilayer. Local lattice parameter measurement and elemental profiles
indicated that some intermixing of Zn and Cd had taken place. The average widths of the ZnTe layer and the (Cd,Zn)Te transition
region were found to be roughly 6.5 nm and 3.5 nm, respectively. 相似文献
16.
We calculated energies required to remove atoms from various configurations on (111), (110), (100), and (211) HgTe surfaces.
The excess pair energies for various species are then calculated and are used in a thermodynamic model to study the growth.
All energies are obtained using a Green’s function method. The pair distributions are calculated from these energies in a
generalized quasi-chemical approximation. The calculated critical temperatures for surface roughness transition are found
to be considerably higher than the usual growth temperature of 185°C, so the growth on these surfaces is expected to be layer-by-layer
with formation of two-dimensional islands. However, among the surfaces studied, only the (211) surfaces have an attractive
binding energy for Hg, making those surfaces suited for better growth. The critical temperature for growth on (21 l)Hg is
slightly higher than that for (211)Te, but we also find that Hg sticking coefficient on (21 l)Hg surface is considerably lower
than that on (21 l)Te surface. These calculations are consistent with the observed higher growth rate of the (211)Te surface.
Our calculations suggest that there will be fewer grown-in vacancies and Te antisites, at the expense of growth rate and sticking
coefficient, for crystals grown on (211)Hg surface. We further calculated the Hg and Te vacancy formation energies as functions
of surface orientations and layer depth. The cation vacancy formation energies from completed surface regions (islands) are
higher than bulk values near anion terminated surfaces and smaller than bulk values near cation terminated surfaces. 相似文献
17.
Kwang-Chon Kim Hyun Jae Kim Sang-Hee Suh M. Carmody S. Sivananthan Jin-Sang Kim 《Journal of Electronic Materials》2010,39(7):863-867
Single-crystalline CdTe(133) films have been grown by metalorganic chemical vapor deposition on Si(211) substrates. We studied
the effect of various growth parameters on the surface morphology and structural quality of CdTe films. Proper oxide removal
from the Si substrate is considered to be the principal factor that influences both the morphology and epitaxial quality of
the CdTe films. In order to obtain single-crystalline CdTe(133) films, a two-stage growth method was used, i.e., a low-temperature
buffer layer step and a high- temperature growth step. Even when the low-temperature buffer layer shows polycrystalline structure,
the overgrown layer shows single-crystalline structure. During the subsequent high-temperature growth, two-dimensional crystallites
grow faster than other, randomly distributed crystallites in the buffer layer. This is because the capturing of adatoms by
steps occurs more easily due to increased adatom mobility. From the viewpoint of crystallographic orientation, it is assumed
that the surface structure of Si(211) consists of (111) terrace and (100) step planes with an interplanar angle of 54.8°.
This surface structure may provide many preferable nucleation sites for adatoms compared with nominally flat Si(100) or (111)
surfaces. The surface morphology of the resulting films shows macroscopic rectangular-shaped terrace—step structures that
are considered to be a (111) terrace with two {112} step planes directed toward 〈110〉. 相似文献
18.
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
19.
J. D. Benson A. J. Stoltz J. B. Varesi L. A. Almeida E. P. G. Smith S. M. Johnson M. Martinka A. W. Kaleczyc J. K. Markunas P. R. Boyd J. H. Dinan 《Journal of Electronic Materials》2005,34(6):726-732
The surface of (211)B HgCdTe has been studied by reflection high-energy electron diffraction (RHEED) and atomic force microscopy
(AFM). RHEED analysis of the as-grown Hg-rich molecular beam epitaxy (MBE) (211)B HgCdTe suggests the surface reconstructs
by additional Hg incorporation. The plasma-etched (211)B HgCdTe surface is crystalline but stepped and facetted. RHEED analysis
indicates asymmetric pyramids (base dimensions ≈0.5×1.1 nm) are formed to minimize surface Hg concentration. The AFM examination
of plasma-etched (211)B HgCdTe reveals oriented mesoscopic features. 相似文献
20.
C. M. Lennon L. A. Almeida R. N. Jacobs J. D. Benson P. J. Smith J. K. Markunas J. Arias J. Pellegrino 《Journal of Electronic Materials》2013,42(11):3344-3348
The surface kinetics of CdTe (211)B grown by molecular beam epitaxy (MBE) is investigated using spectroscopic ellipsometry (SE) during in situ cyclic annealing. A method of measuring sublimation rates from high-index surfaces without use of reflection high-energy electron diffraction is presented. The effect of Te2 overpressure on the activation energy of sublimation for the CdTe (211)B surface is reported. The sensitivity of SE to surface temperature and film thickness was leveraged to monitor sublimation rates of CdTe stabilized by a Te2 overpressure. The sublimation activation energy was found to increase from 0.45 eV to 2.94 eV under the Te2 beam pressure regime investigated. 相似文献