Si/CdTe复合衬底HgCdTe液相外延材料的生长与性能分析

通过改进推舟液相外延技术,成功地在(211)晶向Si/CdTe复合衬底上进行了HgCdTe液相外延生长,获得了表面光亮的HgCdTe外延薄膜.测试结果表明,(211)Si/CdTe复合衬底液相外延HgCdTe材料组分及厚度的均匀性与常规(111)CdZnTe衬底HgCdTe外延材料相当;位错腐蚀坑平均密度为(5～8)×105 cm-2,比相同衬底上分子束外延材料的平均位错密度要低一个数量级;晶体的双晶半峰宽达到70″左右.研究结果表明,在发展需要低位错密度的大面积长波HgCdTe外延材料制备技术方面,Si/CdTe复合衬底HgCdTe液相外延技术可发挥重要的作用.     

Si/CdTe复合衬底HgCdTe液相外延材料的生长与性能分析

通过改进推舟液相外延技术,成功地在(211)晶向Si/CdTe复合衬底上进行了HgCdTe液相外延生长,获得了表面光亮的HgCdTe外延薄膜.测试结果表明,(211)Si/CdTe复合衬底液相外延HgCdTe材料组分及厚度的均匀性与常规(111)CdZnTe衬底HgCdTe外延材料相当;位错腐蚀坑平均密度为(5～8)×105 cm-2,比相同衬底上分子束外延材料的平均位错密度要低一个数量级;晶体的双晶半峰宽达到70″左右.研究结果表明,在发展需要低位错密度的大面积长波HgCdTe外延材料制备技术方面,Si/CdTe复合衬底HgCdTe液相外延技术可发挥重要的作用.     

分子束外延CdTe（211）B／Si复合衬底材料

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．     

CdTe/Si复合衬底Ex-situ退火研究

复合衬底CdTe/ZnTe/Si的晶体质量是导致随后外延的HgCdTe外延膜高位错密度的主要原因之一,因此如何提高复合衬底CdTe/Si晶体质量是确保硅基碲镉汞走上工程化的关键所在。降低复合衬底CdTe/Si位错密度方法一般有:生长超晶格缓冲层、衬底偏向、In-situ退火和Ex-situ退火等,本文主要研究Ex-situ退火对复合衬底CdTe/Si晶体质量的影响。研究表明复合衬底经过Ex-situ退火后位错密度最好值达4.2×105cm-2,双晶半峰宽最好值达60arcsec。     

Si基CdTe复合衬底分子束外延研究

文章引入晶格过渡的Si/ZnTe /CdTe作为复合外延基底材料,以阻挡Si/HgCdTe之间大晶格失配产生的高密度位错。通过对低温表面清洁化、面极性控制和孪晶抑制等的研究,解决了Si基CdTe分子束外延生长中诸多的技术难题。在国内首次采用分子束外延(MBE)的方法获得了大面积的Si基CdTe复合衬底材料,对应厚度为4～4. 4μm Si/CdTe (211)样品双晶半峰宽的统计平均结果为83弧秒,与相同厚度的GaAs/CdTe (211)双晶平均水平相当。     

在兰宝石衬底上金属有机外延生长CdTe和HgCdTe薄膜

红外探测系统中的光敏元件需要HgCdTe外延膜。通常,HgCdTe生长于CdTe衬底上,这种衬底具有能与HgCdTe晶格紧密匹配且又能不受HgCdTe膜自动掺杂影响的诱人性能。但是,CdTe衬底昂贵、脆、不能得到大的面积且与平常得到的衬底如Si、GaAs、Al_2O_3(兰宝石)或InSb相比结晶质量较差。因此需要另选一种基片材料。兰宝石就是一种诱人的候选者,这是因为它的结晶质量高、成本低、有刚度且能得到大的面积。液相外延技术是外延生长HgCdTe用的最普通的技术。然而,由于生长的熔料不能湿润兰宝石衬底,从而防碍了在兰宝石衬底上液相外延生长。为在兰宝石衬底上生长薄膜,最近     

红外探测器材料Ⅱ

一、HgCdTe的外延与分子束外延生长 1.用MOVPE生长在(211)B CdTe/Si衬底上的HgCdTe膜层的特性(S.H.Suh等,韩国科技研究所)     

在InSb和GaAs衬底上用MOCVD法生长CdTe和HgCdTe外延膜

由于HgCdTe的红外探测特性致使生长高质量HgCdTe外延膜具有重要意义。目前一般是在CdTe衬底上生长HgCdTe。CdTe和HgCdTe都是Ⅰ-Ⅵ化合物,具有同样的晶体结构和紧密匹配的晶格。然而,CdTe衬底有缺点。它们价格高,不能制成大面积和不具备高结晶完整性。因此,要求研制在不相同衬底材料上进行HgCdTe外延。最近有文献报导在他种衬底上用分子束外延(MBE)和激光辅助淀积     

Si基CdTe/HgCdTe分子束外延材料的位错抑制

基于GaAs/Si材料中位错的运动反应理论,修正获得CdTe/Si和HgCdTe/Si外延材料中的位错运动反应模型.采用快速退火方法对Si基HgCdTe外延材料进行位错抑制实验研究,实验结果与理论曲线基本吻合,从理论角度解释了不同高温热处理条件对材料体内位错的抑制作用.对于厚度为4～10μnn的CdTe/Si进行500...     

热壁外延生长的CdTe外延层的研究

本文论述了用热壁外延的方法在CdTe体材料衬底上生长CdTe,并且用各种方法对CdTe外延层进行的研究。为提高衬底材料的质量。我们采用热壁外延方法在CdTe体材料衬底上再外延生长—层CdTe缓冲层,如果外延条件适当,缓冲层一般可使体材料的一部分缺陷消除或减少,好的外延层同经过仔细表面处理的体材料衬底一样是镜面的,因此可直接用作外延HgCdTe     

GaSb: A New Alternative Substrate for Epitaxial Growth of HgCdTe

In this work, GaSb is proposed as a new alternative substrate for the growth of HgCdTe via molecular beam epitaxy (MBE). Due to the smaller mismatch in both lattice constant and coefficient of thermal expansion between GaSb and HgCdTe, GaSb presents a better alternative substrate for the epitaxial growth of HgCdTe, in comparison to alternative substrates such as Si, Ge, and GaAs. In our recent efforts, a CdTe buffer layer technology has been developed on GaSb substrates via MBE. By optimizing the growth conditions (mainly growth temperature and VI/II flux ratio), CdTe buffer layers have been grown on GaSb substrates with material quality comparable to, and slightly better than, CdTe buffer layers grown on GaAs substrates, which is one of the state-of-the-art alternative substrates used in growing HgCdTe for the fabrication of mid-wave infrared detectors. The results presented in this paper indicate the great potential of GaSb to become the next generation alternative substrate for HgCdTe infrared detectors, demonstrating MBE-grown CdTe buffer layers with rocking curve (double crystal x-ray diffraction) full width at half maximum of ～60 arcsec and etch pit density of ～10⁶ cm^?2.     

Selective CdTe Nanoheteroepitaxial Growth on Si(100) Substrates Using the Close-Spaced Sublimation Technique Without the Use of a Mask

The development of HgCdTe detectors requires high sensitivity, small pixel size, low defect density, long-term thermal-cycling reliability, and large-area substrates. CdTe bulk substrates were initially used for epitaxial growth of HgCdTe films. However, CdTe has a lattice mismatch with long-wavelength infrared (LWIR) and middle-wavelength infrared (MWIR) HgCdTe that results in detrimental dislocation densities above mid-10⁶ cm^?2. This work explores the use of CdTe/Si as a possible substrate for HgCdTe detectors. Although there is a 19% lattice mismatch between CdTe and Si, the nanoheteroepitaxy (NHE) technique makes it possible to grow CdTe on Si substrates with fewer defects at the CdTe/Si interface. In this work, Si(100) was patterned using photolithography and dry etching to create 500-nm to 1-μm pillars. CdTe was selectively deposited on the pillar surfaces using the close-spaced sublimation (CSS) technique. Scanning electron microscopy (SEM) was used to characterize the CdTe selective growth and grain morphology, and transmission electron microscopy (TEM) was used to analyze the structure and quality of the grains. CdTe selectivity was achieved for most of the substrate and source temperatures used in this study. The ability to selectively deposit CdTe on patterned Si(100) substrates without the use of a mask or seed layer has not been observed before using the CSS technique. The results from this study confirm that CSS has the potential to be an effective and low-cost technique for selective nanoheteroepitaxial growth of CdTe films on Si(100) substrates for infrared detector applications.     

Long wavelength infrared, molecular beam epitaxy, HgCdTe-on-Si diode performance

In the past several years, we have made significant progress in the growth of CdTe buffer layers on Si wafers using molecular beam epitaxy (MBE) as well as the growth of HgCdTe onto this substrate as an alternative to the growth of HgCdTe on bulk CdZnTe wafers. These developments have focused primarily on mid-wavelength infrared (MWIR) HgCdTe and have led to successful demonstrations of high-performance 1024×1024 focal plane arrays (FPAs) using Rockwell Scientific’s double-layer planar heterostructure (DLPH) architecture. We are currently attempting to extend the HgCdTe-on-Si technology to the long wavelength infrared (LWIR) and very long wavelength infrared (VLWIR) regimes. This is made difficult because the large lattice-parameter mismatch between Si and CdTe/HgCdTe results in a high density of threading dislocations (typically, >5E6 cm⁻²), and these dislocations act as conductive pathways for tunneling currents that reduce the R_oA and increase the dark current of the diodes. To assess the current state of the LWIR art, we fabricated a set of test diodes from LWIR HgCdTe grown on Si. Silicon wafers with either CdTe or CdSeTe buffer layers were used. Test results at both 78 K and 40 K are presented and discussed in terms of threading dislocation density. Diode characteristics are compared with LWIR HgCdTe grown on bulk CdZnTe.     

Te-rich liquid phase epitaxial growth of HgCdTe on Si-based substrates

The growth of high quality (111)B oriented HgCdTe layers on CdZnTe/GaAs/Si and CdTe/Si substrates by Te-rich slider liquid phase epitaxy (LPE) is reported. Although the (111) orientation is susceptible to twinning, a reproducible process yielding twin-free layers with excellent surface morphology has been developed. The electrical properties and dislocation density in films grown on these substrates are comparable to those measured in HgCdTe layers grown on bulk CdTe substrates using the same LPE process. This is surprising in view of the large lattice mismatch that exists in these systems. We will report details of both the substrate and HgCdTe growth processes that are important to obtaining these results.     

Recent Progress in MBE Growth of CdTe and HgCdTe on (211)B GaAs Substrates

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.     

Heteroepitaxy of HgCdTe (211)B on Ge substrates by molecular beam epitaxy for infrared detectors

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.     

MBE growth of HgCdTe on silicon substrates for large-area infrared focal plane arrays: A review of recent progress

We review the rapid progress that has been made during the past three years in the heteroepitaxial growth of HgCdTe infrared detector device structures on Si substrates by molecular-beam epitaxy. The evolution of this technology has enabled the fabrication of high performance, large-area HgCdTe infrared focal-plane arrays on Si substrates. A key element of this heteroepitaxial approach has been development of high quality CdTe buffer layers deposited on Si(112) substrates. We review the solutions developed by several groups to address the difficulties associated with the CdTe/Si(112) heteroepitaxial system, including control of crystallographic orientation and minimization of defects such as twins and threading dislocations. The material quality of HgCdTe/Si and the performance of HgCdTe detector structures grown on CdTe/Si(112) composite substrates is reviewed. Finally, we discuss some of the challenges related to composition uniformity and defect generation encountered with scaling the MBE growth process for HgCdTe to large-area Si substrates.