硅基低位错密度厚锗外延层的UHV/CVD法生长

利用超高真空化学气相淀积系统, 基于低温缓冲层和插入应变超晶格的方法, 在Si(100)衬底上外延出厚度约为880 nm的纯Ge层. 采用X射线双晶衍射、高分辨透射电镜、原子力显微镜和光致发光谱分别表征了其结构及光学性质. 测试结果显示外延Ge的X射线双晶衍射曲线半高宽为273", 表面均方根粗糙度为0.24 nm, 位错密度约为1.5×10⁶ cm². 在室温下观测到外延Ge的直接带跃迁光致发光, 发光峰值位于1540 nm. 表明生长的Si基Ge材料具有良好的结晶质量, 可望在Si基光电子器件中得到应用.     

Non-homogeneous SiGe-on-insulator formed by germanium condensation process

Ge condensation process of a sandwiched structure of Si/SiGe/Si on silicon-on-insulator （SOI） to form SiGe-on- insulator （SGOI） substrate is investigated. The non-homogeneity of SiGe on insulator is observed after a long time oxidation and annealing due to an increased consumption of silicon at the inflection points of the corrugated SiGe film morphology, which happens in the case of the rough surface morphology, with lateral Si atoms diffusing to the inflection points of the corrugated SiGe film. The transmission electron microscopy measurements show that the non-homogeneous SiGe layer exhibits a single crystalline nature with perfect atom lattice. Possible formation mechanism of the non-homogeneity SiGe layer is presented by discussing the highly nonuniform oxidation rate that is spatially dependent in the Ge condensation process. The results are of guiding significance for fabricating the SGOI by Ge condensation process.     

N型掺杂应变Ge发光性质

应变锗材料具有准直接带特性,而且与标准硅工艺兼容,成为实现硅基发光器件重要的候选材料之一.本文基于vandeWalle形变势理论,计算了应变情况下半导体Ge材料的能带结构以及载流子在导带中的分布;通过分析载流子直接带和间接带间的辐射复合以及俄歇复合、位错等引起的非辐射复合的竞争,计算了N型掺杂张应变Ge材料直接带跃迁的内量子效率和光增益等发光性质.结果表明,张应变可有效增强Ge材料直接带隙跃迁发光.在1.5%张应变条件下,N型掺杂Ge的最大内量子效率可以达到74.6%,光增益可以与III-V族材料相比拟.     

硅基锗薄膜选区外延生长研究

利用超高真空化学气相沉积系统, 基于低温Ge缓冲层和选区外延技术, 在Si/SiO₂图形衬底上选择性外延生长Ge薄膜. 采用X射线衍射、扫描电镜、原子力显微镜、拉曼散射光谱等表征了其晶体质量和应变等参数随图形尺寸的变化规律. 测试结果显示, 位错密度随着图形衬底外延窗口的尺寸减小而减少, Ge层中的张应变随窗口尺寸的增大先增大而后趋于稳定. 其原因是选区外延Ge在图形边界形成了(113)面, 减小了材料系统的应变能, 而单位体积应变能随窗口尺寸的增加而减少; 选区外延厚度为380 nm的Ge薄膜X射线衍射曲线半高宽为678", 表面粗糙度为0.2 nm, 表明选区生长的Ge材料具有良好的晶体质量, 有望应用于Si基光电集成.     

循环氧化/退火制备GeOI薄膜材料及其性质研究

采用超高真空化学气相淀积系统在SOI(绝缘体上硅)衬底上生长了Si_0.82Ge_0.18外延层,通过循环氧化/退火工艺,制备出Ge组分从0.24到1的绝缘体上锗硅(SGOI)材料.采用高分辨透射电镜、拉曼散射光谱和光致发光谱表征了其结构及光学性质,对氧化过程中SiGe层中的Ge组分和应变的演变进行了分析.最后制备出11 nm厚的绝缘体上Ge材料(GeOI),具有完整的晶格结构和平整的界面.室温下观测到绝缘体上Ge直接带跃迁光致发光,发光峰值位于1540 nm,发光 关键词： GeOI 氧化 退火 光致发光谱     

Analysis of tensile strain enhancement in Ge nano-belts on an insulator surrounded by dielectrics

Ge nano-belts with large tensile strain are considered as one of the promising materials for high carrier mobility metal- oxide-semiconductor transistors and efficient photonic devices. In this paper, we design the Ge nano-belts on an insulator surrounded by Si3N4 or SiO？ for improving their tensile strain and simulate the strain profiles by using the finite difference time domain （FDTD） method. The width and thickness parameters of Ge nano-belts on an insulator, which have great effects on the strain profile, are optimized. A large uniaxial tensile strain of 1.16% in 50-nm width and 12-nm thickness Ge nano-belts with the sidewalls protected by Si3N4 is achieved after thermal treatments, which would significantly tailor the band gap structures of Ge-nanobelts to realize the high performance devices.     

Si/SiGe量子级联激光器的能带设计

详细论述Si/SiGe量子级联激光器的工作原理，通过对比找到一组合适的Si，Ge和SiGe合金的能带参数，进而应用6×6 k·p方法计算了不同阱宽、不同Ge组分Si/Si_1-xGe_x/Si量子阱价带量子化的空穴能级本征值及其色散关系，分析Si/Si_1-xGe_x/Si量子阱空穴态能级间距随阱宽和组分的变化规律，最后应用计算结果讨论了Si/SiGe量子级联激光器有源区的能带设计，有益于优化Si /SiGe量子级联激光器结构. 关键词： 硅锗材料 量子级联激光器 子带跃迁 k·p方法')" href="#">k·p方法     

High-performing silicon-based germanium Schottky photodetector with ITO transparent electrode

A near-infrared germanium(Ge)Schottky photodetector(PD)with an ultrathin silicon(Si)barrier enhancement layer between the indium-doped tin oxide(ITO)electrode and Ge epilayer on Si or silicon-on-insulator(SOI)is proposed and fabricated.The well-behaved ITO/Si cap/Ge Schottky junctions without intentional doping process for the Ge epilayer are formed on the Si and SOI substrates.The Si-and SOI-based ITO/Si cap/Ge Schottky PDs exhibit low dark current densities of 33 mA/cm2 and 44 mA/cm2,respectively.Benefited from the high transmissivity of ITO electrode and the reflectivity of SOI substrate,an optical responsivity of 0.19 A/W at 1550 nm wavelength is obtained for the SOI-based ITO/Si cap/Ge Schottky PD.These complementary metal–oxide–semiconductor(CMOS)compatible Si(or SOI)-based ITO/Si cap/Ge Schottky PDs are quite useful for detecting near-infrared wavelengths with high efficiency.     

氢等离子体气氛中退火多孔硅的表面和光荧光特性

用电化学腐蚀法制备了多孔硅(PS),在氢等离子体气氛中不同温度下对多孔硅样品进行了退火处理,并进行了光致发光(PL)谱和原子力显微镜(AFM)表面形貌的测量。不同退火温度给PS表面形态带来较大变化,也影响了其PL谱特性。在退火的样品中观察到的PL谱高效蓝光和紫光谱带,我们认为主要源于量子限制发光峰和非平衡载流子被带隙中浅杂质能级所俘获而引起的辐射复合所产生的。在420—450℃退火处理的多孔硅的PL谱上观察到了一个未见诸于报道的紫光新谱带(3．24eV,382nm),其发光机理有待于进一步研究。     

Low-temperature plasma enhanced atomic layer deposition of large area HfS_2 nanocrystal thin films

Hafnium disulfide(HfS2) is a promising two-dimensional material for scaling electronic devices due to its higher carrier mobility, in which the combination of two-dimensional materials with traditional semiconductors in the framework of CMOS-compatible technology is necessary. We reported on the deposition of HfS2 nanocrystals by remote plasma enhanced atomic layer deposition at low temperature using Hf(N(CH3)(C2H5))4 and H2S as the reaction precursors. Selflimiting reaction behavior was observed at the deposition temperatures ranging from 150℃ to 350℃, and the film thickness increased linearly with the growth cycles. The uniform HfS2 nanocrystal thin films were obtained with the size of nanocrystal grain up to 27 nm. It was demonstrated that higher deposition temperature could enlarge the grain size and improve the HfS2 crystallinity, while causing crystallization of the mixed HfO2 above 450℃. These results suggested that atomic layer deposition is a low-temperature route to synthesize high quality HfS2 nanocrystals for electronic device or electrochemical applications.