Cubic HfN Thin Films with Low Resistivity on Si (001) and MgO (001) Substrates

We deposited epitaxial and highly textured cubic HfN (B1-NaCl) thin films on single-crystal MgO (001) and Si (001) substrates, respectively, using a pulsed laser deposition technique. The HfN thin films are around 100 nm thick. Detailed microstructural characterizations, including x-ray diffraction, transmission electron microscopy (TEM), and high-resolution TEM, were carried out. Resistivity as low as 40 μΩ cm was observed by standard four-point probe measurements. The low resistivity and good diffusion barrier properties demonstrated by our preliminary Cu-diffusion tests for HfN on Si suggest that HfN could be a promising candidate diffusion barrier for Cu interconnects.     

HWE生长条件对CdTe/Si薄膜结构特性的影响

研究了热壁外延(HWE)生长条件对Si(100)衬底上沉积外延的多晶CdTe薄膜的晶粒尺寸和取向的影响.用SEM和XRD技术分析了不同外延时间、不同衬底温度及不同源温下外延膜的表面形貌和结构特征.SEM发现随着外延时间的增加或衬底温度的提高,晶粒尺寸明显增大;XRD显示所有的外延薄膜均为面心立方结构,并高度显示优势取向(111),且随着衬底温度或薄膜厚度的增加,(111)峰的衍射强度增加,显示薄膜的择优取向更好.其原因是面心立方结构中,(111)表面具有的表面自由能最低.通过对不同外延时间下薄膜厚度的测试发现,薄膜具有加速生长趋势.衬底温度及源温对外延层厚度均有较大的影响.     

在Si(211)衬底上分子束外延CdTe的晶格应变

文章利用高分辨率X射线衍射技术对分子束外延CdTe（211）B/Si（211）材料的CdTe外延薄膜进行了倒易点二维扫描,并通过获得的对称衍射面和非对称衍射面的倒易空间图,对CdTe外延层的剪切应变和正应变状况进行了分析.研究发现,对于CdTe/Si结构,随着CdTe厚度的增加,[1-1-1]、[01-1]两个方向的剪切角γ[1-1-1]和λ[01-1]都有变小的趋势,且γ[1-1-1]的大小约为γ[01-1]的两倍;对于CdTe/ZnTe/Si,ZnTe缓冲层的引入可以有效地降低CdTe层的剪切应变.CdTe层的正应变表现为张应变,主要来源于CdTe和Si的热膨胀系数存在差异,而在从生长温度280℃降至室温20℃的过程产生的热应变.     

Analysis of Mesa Dislocation Gettering in HgCdTe/CdTe/Si(211) by Scanning Transmission Electron Microscopy

Due to its strong infrared absorption and variable band-gap, HgCdTe is the ideal detector material for high-performance infrared focal-plane arrays (IRFPAs). Next-generation IRFPAs will utilize dual-color high-definition formats on large-area substrates such as Si or GaAs. However, heteroepitaxial growth on these substrates is plagued by high densities of lattice-mismatch-induced threading dislocations (TDs) that ultimately reduce IRFPA operability. Previously we demonstrated a postgrowth technique with the potential to eliminate or move TDs such that they have less impact on detector operability. In this technique, highly reticulated mesa structures are produced in as-grown HgCdTe epilayers, and then subjected to thermal cycle annealing. To fully exploit this technique, better understanding of the inherent mechanism is required. In this work, we employ scanning transmission electron microscopy (STEM) analysis of HgCdTe/CdTe/Si(211) samples prepared by focused ion beam milling. A key factor is the use of defect-decorated samples, which allows for a correlation of etch pits observed on the surface with underlying dislocation segments viewed in cross-section STEM images. We perform an analysis of these dislocations in terms of the general distribution, density, and mobility at various locations within the mesa structures. Based on our observations, we suggest factors that contribute to the underlying mechanism for dislocation gettering.     

Si基热氧化Si1-x-yGexCy薄膜的室温光致发光特性

采用等离子体增强化学气相淀积(PECVD)法在Si(100)衬底上淀积一层厚度约为170nm的富Ge高C含量的Si1-x-yGex/Cy薄膜,然后将其分别在800℃和1100℃下湿氧氧化20min.在室温下观测到强烈的光致发光.室温下的光致发光谱(PL谱)测量显示,800℃下氧化后的样品在370nm和396nm附近有两个光致发光带,1100℃下氧化后的样品只在396nm附近有一个光致发光带.396nm附近的发光带可归之于由氧化薄膜中的缺陷O-Si-O(Si20)或O-Ge-O(Ge20)引起的,而370nm附近的发光带与薄膜中Ge-C对发光中心有关.     

Si基热氧化Si1-x-yGexCy薄膜的室温光致发光特性

采用等离子体增强化学气相淀积（ＰＥＣＤ）法在Ｓｉ（１００）衬底上淀积一层厚度约为１７０ｎｍ的富Ｇｅ高Ｃ含量的Ｓｉ、－ｘ－７ＧｅｘＣｙ薄膜，然后将其分别在８００℃和１１００℃下湿氧氧化２０ｍｉｎ。在室温下观测到强烈的光致发光，室温下的光致发光谱（ＰＬ谱）测量显示，８００℃下氧化后的样品在３７０ｎｍ和３９６ｎｍ附近有两个光致发光带，１１００℃下氧化后的样品只在３９６ｎｍ附近有一光致发光带，３９６ｎｍ附     

Terahertz Emission from GaAs Films on Si(100) and Si(111) Substrates Grown by Molecular Beam Epitaxy

We report on the terahertz emission from femtosecond-laser-irradiated GaAs layers grown on Si(100) and Si(111) substrates. The results show that the terahertz emission from GaAs on Si is stronger than that of a semi-insulating bulk GaAs crystal. This increase is attributed to the strain field at the GaAs/Si interface. In the GaAs of the Si(100) sample, the stronger terahertz emission is observed compared with GaAs on Si(111). Moreover, the effect of changing the doping type of the Si substrate from n-type to semi-insulating was also studied and it was found that the terahertz emission intensity of GaAs on semi-insulating Si(100) is stronger than that of GaAs on n-type Si(100). Finally, strong terahertz emission from GaAs on semi-insulating Si(100) was observed not only in the reflection geometry but also in the transmission geometry. These results hold promise for new applications of terahertz optoelectronics.     

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。     

ZnSe薄膜的激子光谱

采用分子束外延(MBE)技术,在GaAs(100)衬底上生长了厚度从O.045到1.4μm的ZnSe薄膜.X射线衍射谱证实,随着薄膜厚度的增加,应变逐步弛豫.测量了低温下样品的反射谱和光致发光谱,观察到轻重空穴的能级在不同应变下的分裂、移动和反转,以及激子极化激元(Polariton)对反射谱的影响.也观察到束缚激子发光随着薄膜厚度的变化规律:束缚在中性受主杂质上的束缚激子发光(I1峰)随着薄膜厚度的增加逐渐变弱直至消失,而束缚在中性施主杂质上的束缚激子发光(I2峰)则随着厚度增加逐渐增强.     

ZnSe薄膜的激子光谱

采用分子束外延 (MBE)技术 ,在 Ga As(1 0 0 )衬底上生长了厚度从 0 .0 4 5到 1 .4μm的 Zn Se薄膜 .X射线衍射谱证实 ,随着薄膜厚度的增加 ,应变逐步弛豫 .测量了低温下样品的反射谱和光致发光谱 ,观察到轻重空穴的能级在不同应变下的分裂、移动和反转 ,以及激子极化激元 (Po-lariton)对反射谱的影响 .也观察到束缚激子发光随着薄膜厚度的变化规律 :束缚在中性受主杂质上的束缚激子发光 (I1峰 )随着薄膜厚度的增加逐渐变弱直至消失 ,而束缚在中性施主杂质上的束缚激子发光 (I2 峰 )则随着厚度增加逐渐增强 .     

Si和GaAs衬底上生成WN_x薄膜(英文)

WNx films with different composition are formed on Si(100) and GaAs (100) by the reactive rf sputtering in a mixed nitrogen-argon gas to study the influence of various conditions upon WNx film,- one of the most promising materials for self-aligned GaAs MESFET. With the increase of the partial pressure ratio of nitrogen gas or the decrease of sputtering pressure, the deposition rate of WNx film decreases and the atomic percentage of N in the film increaces until it is saturated. Annealing at high temperature in flowing H2 gas induces the decreace of atomic percentage of N in WNx film. After annealing at 900℃ for 30 minites in flowing N2 gas, WNx film formed at lower sputtering pressure is found to have W and W2N, and to have W, WN and/or W2N phase at a higher sputtering pressure. AES analysis shows no conspicuous diffusion after annealing. The electrical resisti vity of WNx film decreases by about 75% as compared with that of as-sputtered film.     

Effect of the Crystallographic Orientation of GaSb Films on Their Structural Properties during MBE Heteroepitaxy on Vicinal Si(001) Substrates

Semiconductors - GaSb films are grown by molecular-beam epitaxy using AlSb/As/Si transition layers on vicinal Si(001) substrates miscuted by 6° in (111) plane direction. The effect of GaSb...     

CdTe/GaAs(111)B薄膜的MBE生长研究

采用分子束外延方法,在GaAs(111)B衬底上,生长CdTe薄膜,以求研制出用于液相外延生长碲镉汞(HgCdTe)薄膜的CdTe/GaAs(111)B复合衬底.通过理论分析和实验探索,优化了生长温度和Te/Cd束流比等重要生长参数,获得了质量较好的CdTe薄膜,再通过循环热处理,使CdTe/GaAs(111)B复合衬底的质量得到进一步的提高,X-射线回摆曲线半峰宽(FWHM)有明显的降低.为LPE-HgCdTe薄膜的生长打下了较好基础.     

TEM Characterization of HgCdTe/CdTe Grown on GaAs(211)B Substrates

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.     

Molecular-Beam Epitaxy of Two-Dimensional GaSe Layers on GaAs(001) and GaAs(112) Substrates: Structural and Optical Properties

Semiconductors - The results of studies of the structural and optical properties of two-dimensional GaSe layers grown by molecular-beam epitaxy on GaAs(001) and GaAs(112) substrates using a valve...     

Structure of CdTe(111)B grown by MBE on misoriented Si(001)

Single domain CdTe(111)B has been grown on Si(001) substrates tilted 1^o 2^o, and 4^o toward [110]. All the layers started with a double-domain structure, then a transition from a double- to a single-domain was observed by reflection high energy electron diffraction. A microscopic picture of this transition is presented. We also measured the tilt between CdTe(111)B and Si(001). The result does not follow the tilt predicted by the currently existing model. A new model of the microscopic mechanism of CdTe(111)B growth is presented. New evidence indicates that optimizing the tilt of the substrate surface is very crucial in improving the CdTe(111)B crystal quality.     

Comparison of MBE Growth of InSb on Si (001) and GaAs (001)

We describe the epitaxial growth of InSb films on both Si (001) and GaAs (100) substrates using molecular-beam epitaxy and discuss the structural and electrical properties of the resulting films. The complete 2 μm InSb films on GaAs (001) were grown at temperatures between 340°C and 420°C and with an Sb/In flux ratio of approximately 5 and a growth rate of 0.2 nm/s. The films were characterized in terms of background electron concentration, mobility, and x-ray rocking curve width. Our best results were for a growth temperature of 350°C, resulting in room-temperature mobility of 41,000 cm²/V s.  For the growth of InSb on Si, vicinal Si(001) substrates offcut by 4° toward (110) were used. We investigated growth temperatures between 340°C and 430°C for growth on Si(001). In contrast to growth on GaAs, the best results were achieved at the high end of the range of T _S =  C, resulting in a mobility of 26,100 cm²/V s for a 2 μm film. We also studied the growth and properties of InSb:Mn films on GaAs with Mn content below 1%. Our results showed the presence of ferromagnetic ordering in the samples, opening a new direction in the diluted magnetic semiconductors.     

ZnCl2掺杂n型ZnSe的分子束外延生长

利用分子束外延(MBE)技术,以5N的ZnCl2作为掺杂源,在半绝缘GaAs (001)衬底上异质外延生长ZnSe:Cl单晶薄膜.研究发现,掺入ZnCl2后,ZnSe外延层的结晶质量和表面形貌与本征ZnSe外延层相比变差,双晶X射线摇摆曲线(DCXRC)的ZnSe (004)衍射峰半峰宽(FWHM)从432 arcsec增大到529 arcsec,表面均方根粗糙度(RMS)从3.00 nm增大到3.70nm.当ZnCl2掺杂源炉的温度为170℃时,ZnSe样品的载流子浓度达到1.238×1019 cm-3,可以满足结型器件制作和隧道结材料设计的要求.     

Determining the [001] crystal orientation of CdTe layers grown on (001) GaAs

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.     

Domain epitaxial growth of TiN/Si(001), TiN/GaAs(001), and Si/TiN/Si(001) heterostructures by laser physical vapor deposition: Theory and experiment

We have successfully deposited epitaxial titanium nitride films on (001) silicon and (001) gallium arsenide substrates and multilayer Si/TiN/Si(001) epitaxial heterostructures using pulsed laser (KrF: λ = 248 nm, τ = 25 ns) physical vapor deposition. The deposition of TiN was carried out at a substrate temperature of 600°C on Si(001) and 400°C on GaAs(00l). The interfaces were sharp without any indication of interfacial reaction. The epitaxial relationships were found to be <001> TiN ‖<001> Si on the silicon substrate, <001> Si ‖<001> TiN |<001> Si on the heterostructure, and [1-10] TiN‖[110] GaAs and [001] TiN ‖[110] GaAs on the GaAs substrate. The growth in these large-mismatch systems is modeled and the various energy terms contributing to the growth of these films are determined. The domain matching epitaxy provides a mechanism of epitaxial growth in systems with large lattice mismatch.The epitaxial growth is characterized by domain epitaxial orientation relationships with m lattice constants of epilayer matching with n of the substrate and with a small residual domain mismatch present in the epilayer. This residual mismatch is responsible for a coherent strain energy. The magnitude of compression of Ti-N bond in the first atomic layer, contributing to the chemical free energy of the interface during the initial stages of growth, is found to be a very important factor in determining the orientation relationship. This result was used to explain the differences in the orientaion relationships between TiN/Si and TiN/GaAs systems. The various energy terms associated with the domain epitaxial growth are evaluated to illustrate that the domain epitaxial growth is energetically favorable compared to the lattice mismatched epitaxial growth. The results of this analysis illustrate that the observed variations in the epitaxial growth are consistent with the minimum energy configurations associated with the domain epitaxial growth.