共查询到20条相似文献,搜索用时 31 毫秒
1.
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
2.
研究了利用GaAs作为衬底的HgCdTe MBE薄膜的表面缺陷,发现其中一类缺陷与Hg源中杂质有关。采用SEM对这类缺陷进行正面和横截面的观察,并采用EDX对其正面和横截面进行成分分析。并设计了两个实验:其一,在CdTe/GaAs衬底上,低温下用Hg源照射20min,再在其上继续高温生长CdTe;其二,在CdTe/GaAs衬底上,一直用Hg源照射下高温生长CdTe。两个实验后CdTe表面都出现与HgCdTe表面相比在形状和分布上类似的表面缺陷,采用光学显微镜和SEM对CdTe表面缺陷进行了观察,通过CdTe表面缺陷和HgCdTe表面缺陷的比较,我们证实了这类表面缺陷的成核起源于Hg源中杂质。 相似文献
3.
We discuss various possibilities for determining the orientation of CdTe layers grown on (001) GaAs and in particular, determining
the (001) orientation. This growth orientation is characterized by a three dimensional growth mechanism which controls the
growth in the (111) orientation. We show that a thin layer of ZnTe deposited directly on the oxide free GaAs surface can be
used to determine the (001) orientation, eliminate (111) phases and enhance a two dimensional growth of the CdTe layer, resulting
in an improved crystalline quality and a smooth surface morphology. CdTe layers grown in the (111) direction on oxide free
(001) GaAs substrates contain (111) microtwins and an intermixed (001) phase.
This work is a part of a Ph.D. thesis to be submitted to the Weizmann Institute of Science. 相似文献
4.
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
5.
Epitaxial lateral overgrowth (ELO) of CdTe was carried out on GaAs using silicon nitride as the mask material. Windows were
delineated on silicon, nitride mask deposited on GaAs substrates and CdTe was grown using metalorganic vapor phase epitaxy.
The films were characterized by atomic force microscopy (AFM). It has been shown that highly selective growth of CdTe can
be achieved at temperatures higher than 500 C and pressures lower than 25 torr using silicon nitride as the mask layer. Optimizing
the growth conditions as well as the stripe directions on the substrates enables the growth of ELO-CdTe with a flattop surface
and vertical sidewalls. AFM studies show that ELO-grown CdTe contains large grains with reduced defect densities, but there
seems to be no difference on the films grown on the window region or on the masked region. The results suggest that the growth
mechanism for CdTe growth on GaAs is different from that of ELO-grown GaN. A possible growth model for the patterned CdTe
growth is also proposed. 相似文献
6.
M. A. Folkard G. Shen V. Kumar T. A. Steele D. Rees I. K. Varga D. Carr K. Fueloep B. A. Johnson P. J. Orders R. H. Hartley H. Buskes M. Gal 《Journal of Electronic Materials》1993,22(8):1097-1102
Phase modulated ellipsometric data recorded during molecular beam epitaxial growth of CdTe/HgTe and CdTe/ZnTe superlattices
on (100) and (211)B oriented Cd0.96Zn0.04Te and GaAs substrates are presented. The measurements provide a continuous monitor of the growth process, thickness, growth
rate, compositional data, and evidence of interdiffusion in CdTe/HgTe superlattices at elevated temperatures. The thickness
measurements are independent of growth kinetics and surface orientation and agree well with those obtained from x-ray diffraction
and reflection high energy electron diffraction. Ellipsometry shows that the incorporation of Hg in CdTe is significantly
higher on (100) oriented surfaces than on (211)B oriented surfaces. Fine structure in the data from CdTe/ZnTe superlattices
may be associated with a surface reconstruction during deposition of each CdTe layer. The experimental results for CdTe/HgTe
superlattices compare well with results of thin film multi-layer calculations. The general applicability of ellipsometry as
an in-situ analytical technique for epitaxial growth of a range of semiconductor superlattices is discussed. 相似文献
7.
In this paper, we report on the atomic layer epitaxy (ALE) of CdTe on GaAs and Si by the organometallic vapor phase epitaxial
process at atmospheric pressure. Self-limiting growth at one monolayer was obtained over the temperature range from 250°C
to 320°C, under a wide range of reactant pressure conditions. A study of growth mechanism indicates that DMCd decomposes into
Cd on the surface and the Te precursors react catalytically on the Cd covered surface. We have used this ALE grown layer to
improve the crystal quality and the morphology of conventionally grown CdTe on GaAs. Improvement in the crystal quality was
also observed when ALE CdTe nucleation was carried out on Si pretreated with DETe at 420°C. Atomic layer epitaxy grown ZnTe
was used to obtain (100) oriented CdTe on (100) silicon. 相似文献
8.
9.
S. P. Kozyrev 《Semiconductors》2009,43(7):911-914
A comparative analysis of multiperiod ZnTe/CdTe superlattices with the CdTe quantum dots grown by molecular beam epitaxy on the GaAs substrate with the ZnTe and CdTe buffer layers is carried out. The elastic-stress-induced shifts of eigenfrequencies of the modes of the CdTe- and ZnTe-like vibrations of materials forming similar superlattices but grown on different buffer ZnTe and CdTe layers are compared. The conditions of formation of quantum dots in the ZnTe/CdTe superlattices on the ZnTe and CdTe buffer layers differ radically. 相似文献
10.
M. S. Han T. W. Kang J. H. Leem B. K. Song Y. B. Hou W. H. Baek M. H. Lee J. H. Bahng K. J. Kim J. M. Kim H. K. Kim T. W. Kim 《Journal of Electronic Materials》1997,26(6):507-510
Spectroscopic ellipsometry and photoreflectance measurements on CdTe/GaAs strained heterostructures grown by moleculclr beam
epitaxy were carried out to investigate the effect of the strain and the dependence of the lattice parameter on the CdTe epitaxial
layer thicknesses. Compressive strains exist in CdTe layers thinner than 2 μm. As the strain increases, the value of the critical-point
energy shift increases linearly. These results indicate that the strains in the CdTe layers grown on GaAs substrates are strongly
dependent on the CdTe layer thickness.
Author to whom all correspondence should be addressed. 相似文献
11.
用透射电镜对Hg1-xCdTe/CdTe和CdTe/GaAs两种异质结的横截面进行了观测分析,对异质结附近的某些结构缺陷,如微孪晶的尺寸,几何形态、层错、界面失配位错的组态特征进行了研究,并对多层膜之间的取向差进行了分析,说明在GaAs衬底上用分子束外延法制备的Hg1-xCdxTe/CdTe/GaAs多层膜,就大量结构缺陷而言,CdTe缓冲层对Hg1-xCdxTe外延层起到了屏障作用,在Hg1-x 相似文献
12.
Deformation phenomena of near-surface GaAs layers are studied using surface acoustic waves during the deposition of Au and
the irradiation of the semiconductor surface by the light of a heated evaporator. It is shown that, in the case of Au deposition,
the near-surface layers are plasticized due to the phase transformations in the Au-Ga-As system, while upon irradiation of
the GaAs surface with light, a coarse-grained layer with liquid-like interlayers is formed. As a result, the type of surface
deformations and their relaxation time change. The integral temporal characteristics of the surface acoustic wave, such as
the variation integrals of its rate and dissipated power, reflect the processes occurring on the surface in the real-time
mode. In summary, they reflect the current magnitude of the resulting deformation. The parameters of occurring processes such
as activation energy and relaxation time are determined. 相似文献
13.
首先给 出了利用光电导天线产生的太赫兹波的时域和频域光谱,进而,基于搭建的太赫 兹时域光谱系统, 并采用透射光谱法分别测量了砷化镓类型的三种半导体材料在太赫兹波段的透过率。结果表 明,基于光电导 天线产生的太赫兹波在0~2THz范围内,光谱比较稳定,频率带宽比 较宽;砷化镓半导体材料在0~2.0THz 范围内的透过率的变化相对较小,具有较高的透过率(>60%),并且 明显优于碲化锌以及碲化镉半导体 材料在太赫兹波段的透过率。因此,相比于碲化锌以及碲化镉半导体材料而言,砷化镓半导 体材料更适用于设计宽频带的太赫兹功能器件。 相似文献
14.
W. J. Hamilton J. A. Vigil W. H. Konkel V. B. Harper S. M. Johnson 《Journal of Electronic Materials》1993,22(8):879-885
Epitaxial layers of CdTe were grown by metalorganic chemical vapor deposition on surfaces of single crystal, {100} GaAs which
had been ground, polished, and etched to a spherically shaped done. This dome-shaped surface allowed the morphological and
structural properties of the epitaxial CdTe layers to be determined for all 360° of azimuth and up to 15° of polar angle from
the [100] axis within a single growth experiment. At two growth temperatures, approximately 275 and 375°C, the results show
distinct twofold rotational symmetry in both morphology and crystal perfection as determined by x-ray rocking curve measurement.
Surface morphology is superior at azimuths near tilts toward the <111>A pole. Four-sided pyramidal hillocks appear at other
azimuths and at 0° tilt; the symmetry of the hillocks diminishes as the tilt increases. The orientations for growth which
simultaneously minimize the surface defects and rocking curve full-width half-maximum appear to be at locations on the surface
where the surface normal is tilted 3–4° toward the <111>A or <111>B, depending on the temperature regime chosen. Epitaxial
layers grown on planar wafers of {100}GaAs tilted toward <111>Ga and <111>As show surface morphology essentially identical
to the dome at these orientations. The surface morphology of CdTe growth on GaAs/Si wafers suggests that these layers are
tilted toward the <111>B. 相似文献
15.
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
16.
Kwang-Chon Kim Seung Hyub Baek Hyun Jae Kim Jin Dong Song Jin-Sang Kim 《Journal of Electronic Materials》2012,41(10):2795-2798
Epitaxial CdTe thin films were grown on GaAs/Si(001) substrates by metalorganic chemical vapor deposition using thin GaAs as a buffer layer. The interfaces were investigated using high-resolution transmission electron microscopy and geometric phase analysis strain mapping. It was observed that dislocation cores exist at the CdTe/GaAs interface with periodic distribution. The spacing of the misfit dislocation was measured to be about 2?nm, corresponding to the calculated spacing of a misfit dislocation (2.6?nm) in CdTe/Si with Burgers vector of a[110]/2. From these results, it is suggested that the GaAs buffer layer effectively absorbs the strain originating from the large lattice mismatch between the CdTe thin film and Si substrate with the formation of periodic structural defects. 相似文献
17.
Copper migration in cdte heterojunction solar cells 总被引:1,自引:0,他引:1
H. C. Chou A. Rohatgi N. M. Jokerst E. W. Thomas S. Kamra 《Journal of Electronic Materials》1996,25(7):1093-1098
CdTe solar cells were fabricated by depositing a Au/Cu contact with Cu thickness in the range of 50 to 150Å on polycrystalline CdTe/CdS/SnO2/glass structures. The increase in Cu thickness improves ohmic contact and reduces series resistance (Rs), but the excess Cu tends to diffuse into CdTe and lower shunt resistance (Rsh) and cell performance. Light I-V and secondary ion mass spectros-copy (SIMS) measurements were performed to understand the correlations between the Cu contact thickness, the extent of Cu incorporation in the CdTe cells, and its impact on the cell performance. The CdTe/CdS/SnO2/glass, CdTe/ CdS/GaAs, and CdTe/GaAs structures were prepared in an attempt to achieve CdTe films with different degrees of crystallinity and grain size. A large grain polycrystalline CdTe thin film solar cell was obtained for the first time by selective etching the GaAs substrate coupled with the film transfer onto a glass substrate. SIMS measurement showed that poor crystallinity and smaller grain size of the CdTe film promotes Cu diffusion and decreases the cell performance. Therefore, grain boundaries are the main conduits for Cu migration and larger CdTe grain size or alternate method of contact formation can mitigate the adverse effect of Cu and improve the cell performance. 相似文献
18.
Q. Jiang A. W. Brinkman B. J. Cantwell J. T. Mullins Fabrice Dierre A. Basu P. Veeramani P. Sellin 《Journal of Electronic Materials》2009,38(8):1548-1553
This paper reports on a detailed study of the development of the close space sublimation method, which has been widely used
in the preparation of polycrystalline CdTe/CdS solar cells, as an epitaxial method for the growth of thick CdTe single crystal
films over 200 μm on GaAs and Ge substrates for high-energy radiation detectors. The resulting microscopic growth phenomena in the process
are also discussed in this paper. High-quality single crystalline CdTe thick films were prepared with x-ray rocking curves
full width at half maximum (FWHM) values, which were ∼100 arcsec on Ge substrates and 300 arcsec on GaAs substrates. The quality
of thick films on Ge(100) showed a substantial improvement with nucleation in a Te-rich growth environment. No Te inclusions
in the CdTe films grown on GaAs(211)B and Ge(100) were observed with IR transmission imaging. Photoluminescence of CdTe/Ge
shows a large reduction in the 1.44 eV defect energy bands compared with films grown on GaAs substrates. The film resistivity
is on the order of 1010 Ω cm, and the film displayed some sensitivity to alpha particles. 相似文献
19.
R.N. Jacobs L.A. Almeida J. Markunas J. Pellegrino M. Groenert M. Jaime-Vasquez N. Mahadik C. Andrews S.B. Qadri T. Lee M. Kim 《Journal of Electronic Materials》2008,37(9):1480-1487
It is well known that the large lattice mismatch (>14%) associated with CdTe/Si, CdTe/Ge, and CdTe/GaAs composite substrates,
is a great contributor to large dislocation densities and other defects that limit the performance of HgCdTe-based infrared
detectors. Though thermal expansion mismatch is another possible contributor to material defects, little work has been done
towards documenting and understanding its effects in these systems. Here, we perform studies to determine the relative contributions
of lattice and thermal mismatch to CdTe film characteristics, including dislocation density and residual stress. Unannealed
and thermally cycled films are characterized using x-ray diffraction, defect decoration, and Nomarski and transmission electron
microscopy. For CdTe/Si, the residual stress is consistently observed to be tensile, while for CdTe/Ge and CdTe/GaAs, a compressive
residual film stress is measured. We show based on theoretically predicted stress levels that the experimental measurements
imply the dominance of thermal mismatch in the residual stress characteristics. 相似文献
20.
Li He Xiangliang Fu Qingzhu Wei Weiqiang Wang Lu Chen Yan Wu Xiaoning Hu Jianrong Yang Qinyao Zhang Ruijun Ding Xiaoshuang Chen Wei Lu 《Journal of Electronic Materials》2008,37(9):1189-1199
Results of first-principles calculations and experiments focusing on molecular beam epitaxy (MBE) growth of HgCdTe on the
alternative substrates of GaAs and Si are described. The As passivation on (2 × 1) reconstructed (211) Si and its effects
on the surface polarity of ZnTe or CdTe were clarified by examining the bonding configurations of As. The quality of HgCdTe
grown on Si was confirmed to be similar to that grown on GaAs. Typical surface defects in HgCdTe and CdTe were classified.
Good results for uniformities of full width at half maximum (FWHM) values of x-ray rocking curves, surface defects, and x values of Hg1−x
Cd
x
Te were obtained by refining the demanding parameters and possible tradeoffs. The sticking coefficient of As4 for MBE HgCdTe was determined. The effects of Hg-assisted annealing for As activation were investigated experimentally and
theoretically by examining the difference of the formation energy of AsHg and AsTe. Results of focal-plane arrays (FPAs) fabricated with HgCdTe grown on Si and on GaAs are discussed. 相似文献