共查询到20条相似文献,搜索用时 15 毫秒
1.
M.F. Vilela G.K. Pribil K.R. Olsson D.D. Lofgreen 《Journal of Electronic Materials》2012,41(10):2937-2942
In this work, spectroscopic ellipsometry (SE) is demonstrated as a technique to calibrate growth temperature measurement devices (thermocouples and pyrometers) prior to real mercury cadmium telluride (HgCdTe) growth. A pyrometer is used to control the substrate temperature in molecular beam epitaxy (MBE) for the growth of HgCdTe-based material. It is known that a very narrow optimal growth temperature range exists for HgCdTe, typically ±5°C. A nonoptimal growth temperature will negatively impact on material quality by inducing growth defects, reducing composition uniformity, causing difficulty in controlling doping incorporation, promoting poor electronic properties, and having other adverse effects. Herein, we present a method for measuring and calibrating substrate temperature measurement equipment by using spectroscopic ellipsometry (SE) prior to real HgCdTe growth. This method is easy to implement, nondestructive, and reliable. The proposed method requires one substrate with a surface material with optical properties well known in the temperature range of interest, but not necessarily the same base material as the material to be grown. In the specific case of this work, we use epitaxial CdTe material on top of a Si substrate. This wafer was used to create a database of its optical properties as a function of temperature by using SE. From the collected optical parameters, a model is built and a fit is generated from the SE data collected. The temperature can then be determined by fitting the temperature-dependent SE measurements from this specific CdTe material. The angle offset and surface roughness parameters are also included in the model to account for changes in the average run-to-run angle variations and surface conditions over time. This work does not attempt to obtain an absolute temperature, but rather a reliable and repeatable relative temperature measurement. 相似文献
2.
M. Reddy J. M. Peterson T. Vang J. A. Franklin M. F. Vilela K. Olsson E. A. Patten W. A. Radford J. W. Bangs L. Melkonian E. P. G. Smith D. D. Lofgreen S. M. Johnson 《Journal of Electronic Materials》2011,40(8):1706-1716
This paper presents the status of HgCdTe growth on large-area Si and CdZnTe substrates at Raytheon Vision Systems (RVS). The different technological tools that were used to scale up the growth from 4 inch to 6 inch diameter on Si and from 4 cm × 4 cm to 8 cm × 8 cm on CdZnTe without sacrificing the quality of the layers are described. Extremely high compositional uniformity and low macrodefect density were achieved for single- and two-color HgCdTe layers on both Si and CdZnTe substrates. Finally, a few examples of detector and focal-plane array results are included to highlight the importance of high compositional uniformity and uniformly low macrodefect density of the epitaxial layers in obtaining high operability and low cluster outages in single- and two-color focal-plane arrays (FPAs). 相似文献
3.
F. Erdem Arkun Dennis D. Edwall Jon Ellsworth Sheri Douglas Majid Zandian Michael Carmody 《Journal of Electronic Materials》2017,46(9):5374-5378
Recent advances in growth of Hg1?x Cd x Te films on large-area (7 cm × 7.5 cm) CdZnTe (CZT) substrates is presented. Growth of Hg1?x Cd x Te with good uniformity on large-area wafers is achieved using a Riber 412 molecular beam epitaxy (MBE) tool designed for growth of Hg1?x Cd x Te compounds. The reactor is equipped with conventional CdTe, Te, and Hg sources for achieving uniform exposure of the wafer during growth. The composition of the Hg1?x Cd x Te compound is controlled in situ by employing a closed-loop spectral ellipsometry technique to achieve a cutoff wavelength (λ co) of 14 μm at 78 K. We present data on the thickness and composition uniformity of films grown for large-format focal-plane array applications. The composition and thickness nonuniformity are determined to be <1% over the area of a 7 cm × 7.5 cm wafer. The films are further characterized by Fourier-transform infrared spectroscopy, optical microscopy, and Hall measurements. Additionally, defect maps show the spatial distribution of defects generated during the epitaxial growth of the Hg1?x Cd x Te films. Microdefect densities are in the low 103 cm?2 range, and void defects are below 500 cm?2. Dislocation densities less than 5 × 105 cm?2 are routinely achieved for Hg1?x Cd x Te films grown on CZT substrates. HgCdTe 4k × 4k focal-plane arrays with 15 μm pitch for astronomical wide-area infrared imagers have been produced using the recently developed MBE growth process at Teledyne Imaging Sensors. 相似文献
4.
Influence of Substrate Orientation on the Growth of HgCdTe by Molecular Beam Epitaxy 总被引:1,自引:0,他引:1
An empirical study is reported, wherein HgCdTe was deposited simultaneously on multiple CdZnTe substrates of different orientations
by molecular beam epitaxy. These orientations included the following vicinal surfaces: (115)B, (113)B, (112)B, and (552)B.
Additionally, growth on (111)B was explored. Growth conditions found to be nearly optimalfor the standard (112)B orientation
were selected. Through a series of growth runs, substrate temperature was varied, and the physical properties of the resulting
HgCdTe epilayers were measured. These measurements included Nomarski microscopy, infrared transmission, x-ray diffraction,
and defect decoration etching. The properties of HgCdTe epilayers as a function of temperature were roughly similar for all
vicinal surfaces. Namely, as the temperature increased, the dislocation density decreased. At some critical temperature, the
density of void defects increased dramatically. This critical temperature varied with orientation, the (115)B exhibiting the
lowest critical temperature and the (112)B and (552)B exhibiting the highest. The (115)B, (113)B, and (112)B orientations
exhibited “needlelike” defects on the as-grown HgCdTe surface. The density of these defects decreased with increasing temperature.
The (552)B surface exhibited no such defects and growth behavior nearly identical to the (112)B growthsurface. 相似文献
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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
8.
利用分子束外延(Molecular Beam Epitaxy, MBE)系统生长了In掺杂硅基碲镉汞(Mercury Cadmium Telluride, MCT)材料。通过控制In源温度获得了不同掺杂水平的高质量MCT外延片。二次离子质谱仪(Secondary Ion Mass Spectrometer, SIMS)测试结果表明,In掺杂浓度在1×1015~2×1016 cm-3之间。表征了不同In掺杂浓度对MCT外延层位错的影响。发现位错腐蚀坑形态以三角形为主(沿<■>方向排列),且位错密度与未掺杂样品基本相当。对不同In掺杂浓度的材料进行汞饱和低温处理后,样品的电学性能均有所改善。结果表明,In掺杂能够提高材料的均匀性,从而获得较高的电子迁移率。 相似文献
9.
B. Asici H. C. Eroglu Y. Ergunt A. San S. Ozer 《Journal of Electronic Materials》2018,47(10):5735-5741
High quality CdZnTe substrates with 4% ZnTe mole fraction are used for epitaxial growth of HgCdTe infrared detector layers. Molecular Beam Epitaxy (MBE) growth of HgCdTe epilayers requires high quality surface layer with sub-nanometer surface roughness values as well. We report on the development of a CdZnTe substrate surface preparation process for MBE growth of high quality HgCdTe epilayers. Surface preparation processes were performed on both commercially available CdZnTe substrates and substrates obtained from in-house grown CdZnTe boules. We developed a multi-step substrate surface processing flow to achieve sub-nanometer surface roughness, low total thickness variation (TTV), and wax or slurry residue free CdZnTe substrate surfaces. Each process step was optimized with the aim of removing the subsurface damage caused by the previous process step; so that we reduce the amount of damaged layer needed to be etched prior to epitaxy. Our developed surface preparation process can be applicable to commercially available CdZnTe substrates with high surface roughness and high TTV. This process was also optimized for as-cut CdZnTe slices. We are capable of processing typically 25 mm?×?25 mm CdZnTe substrates with achievable surface roughness values (Rrms) down to below 0.5 nm. 相似文献
10.
N. Feldberg J. D. Aldous P. A. Stampe R. J. Kennedy T. D. Veal S. M. Durbin 《Journal of Electronic Materials》2014,43(4):884-888
The Zn-IV-N2 family of materials represents a potential earth abundant element alternative to conventional compound semiconductor materials that are based on gallium and indium. While both ZnSiN2 and ZnGeN2 have been studied to some degree, very little is known about the narrow-gap member ZnSnN2. Here, we investigate the growth dynamics of crystalline ZnSnN2 through plasma-assisted molecular beam epitaxy. All films exhibit some degree of crystalline order regardless of growth conditions, although significant tin coverage was observed for films grown with low Zn:Sn flux ratio; Zn flux in particular became increasingly problematic at increased substrate temperatures designed to improve crystallinity. Single-crystal material was achieved through careful optimization of growth parameters. Regardless of deposition conditions or substrate choice, however, all films exhibit a monoclinic structure as opposed to the predicted orthorhombic lattice; this can be directly attributed to sublattice disorder. 相似文献
11.
现阶段,大面阵碲镉汞红外焦平面探测器的需求持续增加,面向更大尺寸的碲镉汞材料制备技术成为了研究热点。对4 in硅基碲镉汞材料外延技术进行了研究。通过提升设备参数的稳定性、控制外延片的平整度以及优化材料工艺参数等一系列手段,突破了大尺寸硅基碲镉汞材料工艺的关键技术瓶颈,并制备出了高平整度、高均匀性、低缺陷率、高质量的4 in硅基碲镉汞材料。结果表明,该材料的双晶衍射半峰宽小于等于90 arcsec,表面宏观缺陷密度小于等于100 cm-2,表面平整度小于等于15 μm。 相似文献
12.
对HgCdTe红外探测器CdSexTe1-x衬底材料的分子束外延生长条件、组分调整等进行了简单介绍。生长条件包括生长结构(主要有CdSexTe1-x/CdTe/ZnTe/Si、CdSexTe1-x/ZnTe/GaAs等)、生长温度(300℃左右)、生长厚度(5μm左右)等。组分调整包括分析Se组分随(JSe+JTe)/JCd和JSe/(JSe+JTe)的变化。JSe/(JSe+JTe)值较小时,Se组分较难融入外延层;JSe/(JSe+JTe)值较大时,Se组分增长较迅速。同时,若JSe/(JSe+JTe)值较小,则Se组分增长趋势... 相似文献
13.
文章叙述了第三代红外焦平面中所需求的碲镉汞分子束外延(MBE)的一些研究成
果。对GaAs、Si基大面积异质外延、表面缺陷抑制、p 型掺杂等MBE的主要难点问题进行了阐述。研究表明, 3 in材料的组分均匀性良好,组分x的偏差为0. 5%。晶格失配引发的孪晶缺陷可以通过合适的低温成核方法得到有效的抑制。在GaAs和Si衬底上外延的HgCdTe材料的(422) x射线衍射半峰宽( FWHM)的典型值为60~80arc·sec。大于2μm缺陷的表面密度可以控制在小于300cm- 2水平。研究发现As的表面黏附系数很低,对生长温度十分敏感,在170℃下约为1 ×10- 4。通过合适的退火,可以实现As的受主激活。采用碲镉汞多层材料已试制了长波n2on2p与p2on2n型掺杂异质结器件以及双色红外短波/中波焦平面探测器,本文报道了一些初步结果。 相似文献
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M. Reddy J. M. Peterson S. M. Johnson T. Vang J. A. Franklin E. A. Patten W. A. Radford J. W. Bangs D. D. Lofgreen 《Journal of Electronic Materials》2009,38(8):1764-1770
This paper presents the progress in the molecular beam epitaxy (MBE) growth of HgCdTe on large-area Si and CdZnTe substrates
at Raytheon Vision Systems. We report a very high-quality HgCdTe growth, for the first time, on an 8 cm × 8 cm CdZnTe substrate.
This paper also describes the excellent HgCdTe growth repeatability on multiple 7 cm × 7 cm CdZnTe substrates. In order to
study the percentage wafer area yield and its consistency from run to run, small lots of dual-band long-wave infrared/long-wave
infrared triple-layer heterojunction (TLHJ) layers on 5 cm × 5 cm CdZnTe substrates and single-color double-layer heterojunction
(DLHJ) layers on 6-inch Si substrates were grown and tested for cutoff wavelength uniformity and micro- and macrovoid defect
density and uniformity. The results show that the entire lot of 12 DLHJ-HgCdTe layers on 6-inch Si wafers meet the testing
criterion of cutoff wavelength within the range 4.76 ± 0.1 μm at 130 K and micro- and macrovoid defect density of ≤50 cm−2 and 5 cm−2, respectively. Likewise, five out of six dual-band TLHJ-HgCdTe layers on 5 cm × 5 cm CdZnTe substrates meet the testing criterion
of cutoff wavelength within the range 6.3 ± 0.1 μm at 300 K and micro- and macrovoid defect density of ≤2000 cm−2 and 500 cm−2, respectively, on the entire wafer area. Overall we have found that scaling our HgCdTe MBE process to a 10-inch MBE system
has provided significant benefits in terms of both wafer uniformity and quality. 相似文献
16.
J.G.A. Wehner R.H. Sewell C.A. Musca J.M. Dell L. Faraone 《Journal of Electronic Materials》2007,36(8):877-883
Investigation into resonant-cavity-enhanced (RCE) HgCdTe detectors has revealed a discrepancy in the refractive index of the
CdTe layers grown by molecular beam epitaxy (MBE) for the detectors, compared with the reported value for crystalline CdTe.
The refractive index of the CdTe grown for RCE detectors was measured using ellipsometry and matches that of CdTe with an
inclusion of approximately 10% voids. X-ray measurements confirm that the sample is crystalline and strained to match the
lattice spacing of the underlying Hg(1−x)Cd(x)Te, while electron diffraction patterns observed during growth indicate that the CdTe layers exhibit some three-dimensional
structure. Secondary ion mass spectroscopy results further indicate that there is enhanced interdiffusion at the interface
between Hg(1−x)Cd(x)Te and CdTe when the Hg(1−x)Cd(x)Te is grown on CdTe, suggesting that the defects are nucleated within the CdTe layers. 相似文献
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The understanding of the configurations of the arsenic tetramer (As
t
), dimer (As
d
), and singlet (As
s
) is important to explain the high electrical compensation of molecular beam epitaxy (MBE) samples and the conversion to p-type behavior. In this work, the possible configurations were optimized from density functional calculations for arsenic
defects As
n
(n = 1, 2, and 4) in as-grown HgTe. According to the dominant electronic contribution to the defect formation energies, which
was calculated under Te-rich conditions, the most probable configurations for As
t
, As
d
, and As
s
have been established. The above discussion applies to the neutral arsenic defects. A further study is necessary to consider
the entropy contribution to the defect formation energy. 相似文献