Si基Ge异质结构发光器件的研究进展

近年来,与Si的CMOS工艺相兼容的Ge/Si异质结构发光器件取得很多重要的进展。本文概述了Si基Ge异质结构发光器件的最新成果,如Ge/Si量子点发光二极管、Si衬底上的Ge发光二极管及激光器和Ge/SiGe多量子阱发光二极管,分别描述了这些器件的特点和增强其发光特性的途径。最后展望了Si基Ge异质结构发光器件的发展趋势,指出尽管Si基Ge异质结构发光器件获得了很大的发展,但是器件的发光效率仍然很低,离实用还有一定距离,还需要在材料和器件的结构方面有更多的创新。     

锗硅量子阱中近带边光跃迁的理论和实验研究

本文研究了SiGe/Si量子阱中近带边光跃迁的产生机制,对由杂质无规分布引起的近带边光跃迁给出了一个物理模型。用此模型计算了光跃迁偶极矩,给出了跃迁偶极矩的上限。提出了未掺杂SiGe/Si量子阱中近带边光跃迁的一种跃迁机制,认为是Ge原子周围波函数畸变的集体行为。用MBE方法生长了掺杂SiGe/Si量子阱材料,在低温下观测到近带边光跃迁。     

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     

应变SiGe SOI量子阱沟道PMOSFET阈值电压模型研究

在绝缘层附着硅(SOI)结构的Si膜上生长SiGe合金制作具有SiGe量子阱沟道的SOI p型金属氧化物半导体场效应晶体管(PMOSFET)，该器件不仅具有SOI结构的优点，而且因量子阱中载流子迁移率高，所以进一步提高了器件的性能.在分析常规的Si SOI MOSFET基础上，建立了应变SiGe SOI 量子阱沟道PMOSFET的阈值电压模型和电流-电压(I-V)特性模型，利用Matlab对该结构器件的I-V特性、跨导及漏导特性进行了模拟分析，且与常规结构的器件作了对比.模拟结果表明，应变SiGe SOI量子阱沟道PMOSFET的性能均比常规结构的器件有大幅度提高. 关键词： 应变SiGe SOI MOSFET 阈值电压 模型     

多晶SiGe栅量子阱pMOSFET阈值电压模型

本文基于多晶SiGe栅量子阱SiGe pMOSFET器件物理,考虑沟道反型时自由载流子对器件纵向电势的影响,通过求解泊松方程,建立了p+多晶SiGe栅量子阱沟道pMOS阈值电压和表面寄生沟道开启电压模型.应用MATLAB对该器件模型进行了数值分析,讨论了多晶Si_1-yGe_y栅Ge组分、Si_1-xGe_x量子阱沟道Ge组分、栅氧化层厚度、Si帽层厚度、沟道区掺杂浓度和 关键词： 多晶SiGe栅 寄生沟道 量子阱沟道 阈值电压     

支撑光网络发展的硅基光电子技术研究

作为大规模集成电路和化合物半导体光电子器件的制造技术共同构成的一门高新技术 ,硅基光电子技术越来越受到重视 .文章着重介绍中国科学院半导体研究所外延生长SiGe/Si量子结构和Si基器件研究的结果 :采用自行设计的UHV/CVD系统 ,成功地生长出Ⅱ型SiGe/Si量子阱和量子点 ,直到 2 5 0K仍能观察到自组织生长Ge/Si(0 0 1 )量子点的发光峰 ;研制成功SiGe/Si谐振腔增强型光电二极管 (RCEPD)、Y分支MZI光调制器和多模干涉 -马赫 -曾德干涉型光开关等Si基光电子器件 ;1 .3μm处RCEPD的量子效率达到 4 .2 % ,- 5V偏压下暗电流密度 1 2 pA/ μm2 ;2× 2热光型光开关的响应时间小于 2 0 μs,两输出端关态串扰为 - 2 2dB ,通态串扰为 - 1 2dB .     

带隙法测定SiGe/Si材料的应变状态

从固体模型理论的结果出发，计算了生长于Si（100）衬底上x值小于085的Si_1-xGe_x合金材料（能带结构为类Si结构）的间接带隙与应变的关系，结 果表明，应变的S iGe材料的带隙和完全弛豫状态下材料的带隙之差与应变呈线性关系.基于这一结果，提出了 用测量带隙来间接测定SiGe/Si应变状态的方法.用带隙法和x射线双晶衍射法测量了不同应 变状态下的SiGe/Si多量子阱材料的应变弛豫度，两者可以较好的符合，表明带隙法测量SiG e应变弛豫度是可行的. 关键词： SiGe合金 应变 带隙     

SiGe电荷注入晶体管的直流特性模型

为了能直观地体现SiGe/Si电荷注入晶体管的收集极电流与漏源电压的关系，利用输入端SiGe/Si量子阱中二维空穴气的隧道模型，建立起此类器件的输入输出数学模型，并利用MATLAB软件对所建模型进行了模拟，结果显示在漏源电压约为1.5 V时，漏电流出现较强的负微分电阻效应，与文献报道结果符合. 关键词： SiGe/Si异质结 电荷注入晶体管 二维空穴气 隧道效应     

应变Si沟道nMOSFET阈值电压模型

在研究分析弛豫SiGe衬底上的应变Si 沟道nMOSFET纵向电势分布的基础上,建立了应变Si nMOSFET阈值电压模型,并利用该模型对不同的器件结构参数进行仿真,获得了阈值电压与SiGe层掺杂浓度和Ge组分的关系、阈值电压偏移量与SiGe层中Ge组分的关系、阈值电压与应变Si层掺杂浓度和厚度的关系. 分析结果表明：阈值电压随SiGe层中Ge组分的提高而降低,随着SiGe层的掺杂浓度的提高而增大;阈值电压随应变Si层的掺杂浓度的提高而增大,随应变Si层厚度增大而增大. 该模型为应变Si 器件阈值电压设计 关键词： 应变硅 阈值电压 电势分布 反型层     

量子阱Si/SiGe/Sip型场效应管阈值电压和沟道空穴面密度模型

Si材料中较低的空穴迁移率限制了Si互补金属氧化物半导体器 件在高频领域的应用. 针对SiGe p型金属氧化物半导体场效应管(PMOSFET)结构, 通过求解纵向一维泊松方程,得到了器件的纵向电势分布, 并在此基础上建立了器件的阈值电压模型,讨论了Ge组分、缓冲层厚度、 Si帽层厚度和衬底掺杂对阈值电压的影响.由于SiGe沟道层较薄, 计算中考虑了该层价带势阱中的量子化效应. 当栅电压绝对值过大时, 由于能带弯曲和能级分裂造成SiGe沟道层中的空穴会越过势垒到达Si/SiO₂界面, 从而引起器件性能的退化. 建立了量子阱SiGe PMOSFET沟道层的空穴面密度模型, 提出了最大工作栅电压的概念, 对由栅电压引起的沟道饱和进行了计算和分析. 研究结果表明,器件的阈值电压和最大工作栅压与SiGe层Ge组分关系密切, Ge组分的适当提高可以使器件工作栅电压范围有效增大.     

ELECTRO-LUMINESCENCE AND PHOTO-LUMINESCENCE FROM STRAINED SiGe/Si QUANTUM WELL

Photo-luminescence and electro-luminescence from step-graded index SiGe/Si quantum well grown by molecular beam epitaxy is reported. The SiGe/Si step-graded index quantum well structure is beneficial to the enhancing of electro-luminescence. The optical and electrical properties of this structure are discussed.     

Self-adjusting formation of a lateral confinement potential in Si/SiGe heterostructures with compensatingpnlayers

We have developed a new concept to create a lateral confinement potential in a two-dimensional electron gas at the interface of a Si/SiGe heterostructure. The method is based on the compensation of then-type doping layer by an additionalp-type layer in a structure similar to a modulation-doped field-effect transistor. A numerical calculation shows that an initially depleted quantum well at zero temperature can be populated by reducing the top-layer thickness. A lateral quantum well is created below a graded step preferentially etched into thep-type layer. Beneath an etched V groove a lateral confinement is obtained with level separation in excess of 8 meV. Similar confinement is achieved in a δ-doped structure with an etch-stop controlled shallow groove.     

Intraband photoresponse of SiGe quantum dot/quantum well multilayers

In this contribution we study the intravalence band photoexcitation of holes from self-assembled Ge quantum dots (QDs) in Si followed by spatial carrier transfer into SiGe quantum well (QW) channels located close to the Ge dot layers. The structures show maximum response in the important wavelength range 3–5 μm. The influence of the SiGe hole channel on photo- and dark current is studied depending on temperature and the spatial separation of QWs and dot layers. Introduction of the SiGe channel in the active region of the structure increases the photoresponsivity by up to about two orders of magnitude to values of 90 mA/W at T=20 K. The highest response values are obtained for structures with small layer separation (10 nm) that enable efficient transfer of photoexcited holes from QD to QW layers. The results indicate that Si/Ge QD structures with lateral photodetection promise very sensitive large area mid-infrared photodetectors with integrated readout microelectronics in Si technology.     

SiGe/Si多量子阱中的光致子带间吸收研究

本文论述了硅锗量子阱中的光致子带间吸收的机理,并在实验中探测SiGe/Si量子阱价带间的红外光致吸收.载流子由氩离子激光器作为光泵浦源产生,所导致的红外吸收由一个步进式傅里叶变换光谱仪来探测.在硅锗量子阱中的光致吸收有两个来源:类似单一掺杂的SiGe薄层的体吸收的自由载流子吸收,及量子阱价带的子带间吸收.实验探测了TE和TM偏振方向的吸收.TM偏振方向的吸收是由偏离布里渊带中心的载流子的跃迁所造成的.我们认为这种光致吸收技术在研究价带耦合效应及其对子带间吸收的影响是非常有效的.     

Current gain and external quantum efficiency modeling of GeSn based direct bandgap multiple quantum well heterojunction phototransistor

This paper aims to provide the performance characteristics of proposed, strain balanced direct band gap multiple quantum wells (MQWs) hetero phototransistor (HPT) made of SiGeSn/GeSn alloys grown on Si substrate which is compatible with recent CMOS fabrication technology. This also presents a comprehensive comparison of this proposed structure with the existing HPT structure made of indirect gap Ge/SiGe MQWs. Alloys of Ge and Sn grown on Si platform shows about tenfold increase in absorption over Ge at C and L-bands due to direct nature of band gap in GeSn. Initial work begins the solution of continuity equation to solve the different terminal current densities and optical gain of the multiple quantum well structure. Main analysis was concentrated on finding the external quantum efficiency depending on the doping variations of emitter and base, base width etc. Finally the photocurrent density variations are estimated for the structure and compared with existing indirect band gap HPT. The calculated values for direct band gap GeSn HPT device are found to be comparable with those for indirect band gap SiGe device to flourish as a potential candidate of photo detectors for the present day telecommunication network.     

Absorption measurement of strained SiGe nanostructures deposited by UHV-CVD

In order to obtain a low band gap photocell based on the widely spread silicon technology, e.g. for thermophotovoltaics, SiGe nanostructures can be introduced into a monocrystalline silicon photocell. Beforehand, it is necessary to know the absorption coefficient of the SiGe quantum wells. On a silicon (1 0 0) substrate multiple Si/SiGe quantum well structures were grown by UHV-CVD. The Ge concentration and the well width were used as growth parameters. To obtain significant absorption, the experiment was set up to allow for 200 internal reflections.The total reflection of the light results in a standing electromagnetic wave. The absorption coefficient was obtained from the experimental data taking the geometry and the electric field distribution in the absorbing layer into account. The influence of well width and germanium content on the absorption was investigated with the goal of maximizing the absorption for photons with energies below the band gap energy of silicon. The measurement results are compared with a theoretical model, which takes the band structure of strained SiGe including confinement effects into account.     

Realization of silicon quantum wires based on Si/SiGe/Si heterostructure

We report on the successful fabrication of silicon quantum wires with SiO2 boundaries on SiGe/Si heterostructures by combining Si/SiGe/Si heteroepitaxy, selective chemical etching, and subsequent thermal oxidation. The observational result of scanning electron microscope is demonstrated. The present method provides a well-controllable way to fabricate silicon quantum wires.