超高真空化学气相沉积外延生长锗硅材料及其应用

综述了硅基锗硅薄膜的外延生长技术、设备及其在光电子器件上的应用,其中着重介绍了超高真空化学气相沉积系统(UHVCVD)。目前来说,UHVCVD是产业化制备高质量锗硅材料的最佳选择。     

UHV/CVD外延生长锗硅碳三元合金中碳的应变缓解效应

碳的加入为Si-Ge系统在能带和应变工程上提供了更大的灵活性.处于替代位置的碳可以缓解SiGe合金的应变,同时调节其能带.报道了用UHV/CVD生长的掺碳达2.2％的锗硅碳合金,获得了良好的外延层质量,应变缓解效应明显.使用了X射线衍射(XRD),二次离子质谱(SIMS)与高分辨电子透射显微镜(HRTEM)对外延层进行检测;使用傅里叶红外吸收光谱(FTIR)确定碳原子处于替代位置,并对实验结果进行了讨论.     

硅缓冲层提高选区外延生长硅基锗薄膜质量

研究了Si缓冲层对选区外延Si基Ge薄膜的晶体质量的影响。利用超高真空化学气相沉积系统,结合低温Ge缓冲层和选区外延技术,通过插入Si缓冲层,在Si/SiO_2图形衬底上选择性外延生长Ge薄膜。采用X射线衍射(XRD)、扫描电子显微镜(SEM)、原子力显微镜(AFM)表征了Ge薄膜的晶体质量和表面形貌。测试结果表明,选区外延Ge薄膜的晶体质量比无图形衬底外延得到薄膜的晶体质量要高;选区外延Ge薄膜前插入Si缓冲层得到Ge薄膜具有较低的XRD曲线半高宽以及表面粗糙度,位错密度低至5.9×10~5/cm^2,且薄膜经过高低温循环退火后,XRD曲线半高宽和位错密度进一步降低。通过插入Si缓冲层可提高选区外延Si基Ge薄膜的晶体质量,该技术有望应用于Si基光电集成。     

UHV/CVD外延生长锗硅碳三元合金中碳的应变缓解效应

碳的加入为 Si- Ge系统在能带和应变工程上提供了更大的灵活性 .处于替代位置的碳可以缓解 Si Ge合金的应变 ,同时调节其能带 .报道了用 UHV/CVD生长的掺碳达 2 .2 %的锗硅碳合金 ,获得了良好的外延层质量 ,应变缓解效应明显 .使用了 X射线衍射 ( XRD) ,二次离子质谱( SIMS)与高分辨电子透射显微镜 ( HRTEM)对外延层进行检测 ;使用傅里叶红外吸收光谱( FTIR)确定碳原子处于替代位置 ,并对实验结果进行了讨论     

UHVCVD外延设备的热场设计

介绍了超高真空化学气相沉积(UHVCVD)锗硅外延设备的加热室设计方法,完善了相关的炉体设计,相关温度指标达到设计标准。     

超高真空化学气相生长用于应变硅的高质量SiGe缓冲层

采用UHV/CVD技术,以多层SiGe/Si结构作为缓冲层来生长应变弛豫SiGe虚衬底,并在此基础上生长出了具有张应力的Si层.利用高分辨X射线、二次离子质谱仪和原子力显微镜分别对薄膜的晶体质量、厚度以及平整度进行了分析.结果表明,通过这种方法制备的SiGe虚衬底,不仅可以有效提高外延层中Ge含量,以达到器件设计需要,而且保证很好的晶体质量和平整的表面.Schimmel液腐蚀后观察到的位错密度只有1×106cm-2.     

超高真空化学气相生长用于应变硅的高质量SiGe缓冲层

采用UHV/CVD技术,以多层SiGe/Si结构作为缓冲层来生长应变弛豫SiGe虚衬底,并在此基础上生长出了具有张应力的Si层.利用高分辨X射线、二次离子质谱仪和原子力显微镜分别对薄膜的晶体质量、厚度以及平整度进行了分析.结果表明,通过这种方法制备的SiGe虚衬底,不仅可以有效提高外延层中Ge含量,以达到器件设计需要,而且保证很好的晶体质量和平整的表面.Schimmel液腐蚀后观察到的位错密度只有1×106cm-2.     

用于SiGe材料生长的新型UHV/UV/CVD系统

介绍了新近研制的用于ＳｉＧｅ材料生长的超高真空（ＵＨＶ）／紫外光（ＵＶ）／能量辅助ＣＶＤ工艺系统。     

MOCVD外延生长GaN材料的技术进展

第三代半导体材料GaN由于具有优良性质使其在微电子和光电子领域有广阔的应用前景,目前制备GaN的方法主要有分子束(MBE)、氯化物气相外延(HVPE)、金属有机物化学气相沉积(MOCVD)。其中HVPE技术制备GaN的速度最快,适合制备衬底材料;MBE技术制备GaN的速度最慢;而MOCVD制备速度适中。因而MOCVD在外延生长GaN材料方面得到广泛应用。介绍了MOCVD法外延生长GaN材料的基本理论、发展概况、利用MOCVD法外延生长GaN材料的技术进展。认为应结合相关技术发展大面积、高质量GaN衬底的制备技术,不断完善缓冲层技术,改进和发展横向外延技术,加快我国具有国际先进水平的MOCVD设备的研发速度,逐步打破进口设备的垄断。     

低温低真空CVD生长锗硅异质结外延材料

利用自行研制的超净低温低真空化学气相外延系统,应用锗烷和硅烷气本,在２英雨到３英雨的衬底硅片上生长了锗硅异质结外延层。在６６５℃,６１０℃和５７５℃不同温度分别生长了Ｓｉ０．５Ｇｅ０．２,Ｇｅ０．５和Ｓｉ０．６５Ｇｅ０．３５的异质外延层,获得了原子级表面和界面的异质外延材料。结果表明：外延生长速率和Ｇｅ组分由硅烷和锗烷的分压及生长时的温度控制。并利用Ｘ射线双昌衍射,扩展电阻和电化学Ｃ－Ｖ法研究了Ｇ     

采用低温缓冲层技术在Si衬底上生长高质量Ge薄膜

采用低温缓冲层技术,在Si衬底上生长了质量优良的Ge薄膜。利用原子力显微镜（AFM）、双晶X射线衍射（XRD）和拉曼散射等研究了薄膜的晶体质量。结果表明,由于无法抑制三维岛状生长,低温Ge缓冲层的表面是起伏的。然而,Ge与Si间的压应变几乎完全弛豫。当缓冲层足够厚时,后续高温Ge外延层的生长能够使粗糙的表面变得平整。在...     

Growth and characterization of germanium and boron doped silicon epitaxial films

The epitaxial growth and characterization of in-situ germanium and boron (Ge/B) doped Si epitaxial films is described. As indicated by secondary ion mass spectroscopy and spreading resistance measurements, the total and electrically activated B concentrations are essentially identical and independent of Ge incorporation. The B and Ge concentrations are uniformly distributed in these Ge/B doped films. A slight enhancement of Hall mobility is obtained, possibly due to the stress relief induced by Ge counterdoping. Carrier conduction in these films is due to the activated B with an activation energy of 0.04 eV as revealed by conductivity versus temperature measurements. Ge atoms appear to be isoelectronic with Si atoms in these films. A slight degradation of minority carrier diffusion length is observed. Electrical characterization of PN diodes on these Ge/B doped films do not reveal any anomaly. SiO₂ on these Ge/B doped films has similar oxide fixed charge density, interface state density and dielectric breakdown strength compared to silicon dioxide on boron doped epitaxial films. Electron injection reveals a different transport mechanism of the SiO₂ grown on these Ge/B doped films.     

Ge预非晶化硅化物工艺的研究

对全耗尽SOI CMOS技术中的Ge预非晶化硅化物工艺进行了研究．Ge的注入，使Si非晶化，减小了硅化物的形成能量．Ti硅化物在非晶层上形成．与传统的Ti硅化物相比，注Ge硅化物工艺有两个明显的特点：一是硅化物形成温度较低；二是硅化物厚度容易控制．采用注Ge硅化物工艺，使源漏薄层电阻约为5.2Ω/□．经过工艺流片，获得了性能良好的器件和电路，其中，当工作电压为5V时，0.8μm 101级环振电路延迟为45ps．     

微腔调制常温Ge量子点光致发光特性

报道了微腔对Ge量子点常温光致发光的调制特性. 生长在SOI硅片上的Ge量子点的常温光致发光呈多峰分布，随波长增加，峰与峰之间的间隔增加. 这种多峰结构与SOI硅片所形成的微腔有关，只有满足特定波长的光致发光才能透出腔体并被探测器搜集. 模拟结果与实验结果吻合得很好，变功率实验也进一步证实了该结论.     

Deposition,post-deposition annealing,and characterization of epitaxial Ge films grown on Si(100) by pyrolysis of GeH4

As a first step towards developing heterostructures such as GaAs/Ge/Si entirely by chemical vapor deposition, Ge films have been deposited on (100) Si by the pyrolysis of GeH₄. The best films are grown at 700° C and are planar and specular, with RBS minimum channeling yields of ≈4.0% (near the theoretical value) and defect densities of 1.3 x 10⁸ cm⁻². Variations of in-situ cleaning conditions, which affect the nature of the Si substrate surface, greatly affect the ability to get good epitaxial growth at 700° C. The majority of the defects found in the Ge films are extrinsic stacking faults, formed by dissociation of misfit and thermal expansion accommodation dislocations. The stacking fault density is not significantly reduced by post-deposition annealing, as is the case for the dislocations observed in MBE Ge films. It is suggested that lowering the CVD growth temperature through the use of high vacuum deposition equipment would result in dislocation defects like those of MBE films which could then be annealed more effectively than stacking faults. Films with defect densities equivalent to MBE Ge films (~2 x 10⁷ cm⁻²) could then probably be produced.     

Si基外延Ge薄膜中残余应变的检测与分析

研究了Si衬底上外延Ge薄膜中的应变。在超高真空化学气相沉积系统中生长Ge薄膜,采用高精度X射线衍射(XRD)和拉曼散射光谱检测薄膜的组份和应变。结果表明,外延薄膜的组份为纯Ge,没有Si的扩散;Ge薄膜中存在少量应变。Ge薄膜XRD峰位和拉曼散射峰位的偏移是由残余应变引起的。定量计算了热膨胀失配引入的张应变和晶格失配引入的压应变与Ge薄膜生长参数的关系,张应变随着生长温度的升高而近似线性增加,压应变随着生长厚度的增加按反比例减小,Ge薄膜最终应变状态由两者共同决定。理论计算值与实验结果吻合良好。     

Ge/Si量子点的控制生长

采用离子束溅射技术,在生长了Si缓冲层的硅晶片上制备了一系列Ge量子点样品.借助原子力显微镜(AFM)和Raman光谱等测试手段研究了Ge/Si量子点生长密度、尺寸及排列均匀性的演变规律.结果表明,改变Si缓冲层厚度及其生长方式,可以有效控制量子点的尺寸、均匀性和密度.随缓冲层厚度增大,量子点密度先增大后减小,停顿生长有利于提高缓冲层结晶性,从而提高量子点的密度,可以达到1.9×1010 cm-2.还研究了Si缓冲层在Ge量子点生长过程中的作用,并提出了量子点的生长模型.     

多层Ge量子点的生长及其光学特性

用超高真空化学气相淀积系统在Si(1 0 0 )衬底上生长了多层Ge量子点.分别用TEM和AFM分析了埋层和最上层量子点的形貌和尺寸,研究了量子点层数和Si隔离层厚度对上层Ge量子点的形状和尺寸分布的影响.观察到样品的低温PL谱线有明显蓝移(87meV) ,Ge量子点的PL谱线的半高宽度(FWHM )为46meV ,说明采用UHV/CVD生长的多层量子点适合量子光电器件的应用     

Growth and characterization of GaAs films deposited on Ge/Si composite substrates by metalorganic chemical vapor deposition

We report the results of studies which have been made on heteroepitaxial layers of GaAs and AlGaAs grown by metalorganic chemical vapor deposition on composite substrates that consist of four different types of heteroepitaxial layered structures of Ge and Ge-Si grown by molecular beam epitaxy on (100)-oriented Si substrates. It is found that of the four structures studied, the preferred composite substrate is a single layer of Ge ∼1 μm thick grown directly on a Si buffer layer. The double-crystal X-ray rocking curves of 2 μm thick GaAs films grown on such substrates have FWHM values as small as 168 arc sec. Transmission electron micrographs of these Ge/Si composite substrates has shown that the number of dislocations in the Ge heteroepitaxial layer can be greatly reduced by an anneal at about 750° C for 30 min which is simultaneously carried out during the growth of the GaAs layer. The quality of the GaAs layers grown on these composite substrates can be greatly improved by the use of a five-period GaAs-GaAsP strained-layer superlattice (SLS). Using the results of these studies, low-threshold optically pumped AlGaAs-GaAs DH laser structures have been grown by MOCVD on MBE Ge/Si composite substrates.     

Growth and characterization of superconducting V3Si on Si and Al2O3 by molecular beam epitaxial techniques

A study of the growth parameters governing the nucleation of metastable superconducting A15 V₃Si on Si and A1₂O₃ is presented. Nominally, 500Å films of V_1-xSi_x were produced through codeposition of V and Si onto heated (111) Si and (1102) A1₂O₃ substrates. Samples were prepared in a custom-built ultrahigh vacuum (UHV) chamber containing dual e-beam evaporation sources and a high temperature substrate heater. V and Si fluxes were adjusted to result in the desired average film composition. V_0.75Si_0.25 films prepared at temperatures in excess of 550° C on Si show significant reaction with the substrate and are nonsuperconducting while similar films grown on A1₂O₃ exhibit superconducting transition temperatures(@#@ T_c @#@) approaching bulk values for V₃Si (16.6-17.1 K). Codeposition at temperatures between 350 and 550° C results in superconducting films on Si substrates while growth at lower temperatures results in nonsuperconducting films. Lowering the growth temperature to 400° C has been shown throughex situ transmission electron microscopy (TEM) and Auger compositional profiling to minimize the reaction with the Si substrate while still activating the surface migration processes needed to nucleate A15 V₃Si. Variation of film composition aboutx = 0.25 is shown to result in nonsuperconducting films for highx and superconducting films with T_c approaching the bulk V value (5.4 K) for lowx. Finally, lowering the V_0.75Si_0.25 deposition rate is shown to raise T_c.