Si/Ge异质结构的生长与特性

<正> 近年来,由Ge,Si这两种晶格失配(4.2％)材料组成的Ge/Si异质结构与Ge/Si应变超晶格,由于共具有重要的科学与技术价值,受到了人们高度重视。分子束外延(MBE)技术已成功地用于生长Ge/Si异质结构和超薄Ge/Si超晶格以及GexSi1-x/Si超晶格。化学汽相淀积技术(CVD)与MBE相比,除了设备简单、价格便宜外,对于Ge,Si外延来说,还便于与现有的硅大规模集成工艺技术相结合,使之更富有实用性。近期已有报道用CVD技术生长GexSi1-x/Si异质结构。     

Ge/Si超晶格喇曼谱研究

我们用喇曼光散射的方法,观察了应变层超晶格的折迭声学声子,从而验证了材料的超晶格多层结构.将实验中观察到的频率和理论计算值进行比较表明,所研究样品的标称值和喇曼实验是基本相符合的.根据光学限制模的频率移动,估算了超晶格样品中Ge层和Si层的应变分布.     

Si／Ge应变层异质结价带偏移的剪裁与设计

讨论应变层异质结价带偏移的剪裁、设计方法，研究Ｓｉ／Ｇｅ应变层异质结价带偏移设计参数与应变条件的关系，基于异质结中平均键能“对齐”，得到适用于Ｓｉ／Ｇｅ异质结价带偏移剪裁与设计的计算公式和图表。     

磁控溅射Ge/Si多层膜的发光特性研究

采用磁控溅射技术,在Si(100)衬底上制备了一系列不同周期、不同Ge层厚度的Ge/Si多层膜样品.用室温光致发光(PL)、Raman散射和AFM图谱对样品进行表征.结果表明:Ge/Si多层膜中的PL发光峰主要来自于Ge晶粒,并且Ge晶粒生长的均匀性对PL发光影响较大,生长均匀的Ge晶粒中量子限域效应明显,随着晶粒的减小,PL发光主峰发生蓝移;在Ge晶粒均匀性较差时,PL发光峰强度较弱,量子限域效应不明显.     

Ge/Si(001)多层纳米岛材料的快速热退火特性

通过X射线双晶衍射、光致发光谱等手段,系统研究了Ge/Si(001)多层纳米岛材料的快速热退火特性.研究表明:退火过程中纳米岛区的Ge/Si原子互扩散作用比浸润层区强烈;并且随着退火时间增加,这种互扩散作用加大,晶体质量下降,影响材料性能.而在800℃退火12s,材料保持了较小的Ge/Si原子互扩散水平和较高的晶体质量,并且经硼离子注入后的样品在这一条件退火后,超过50%的杂质原子可被激活.     

Ge/Si(001)多层纳米岛材料的快速热退火特性

通过X射线双晶衍射、光致发光谱等手段,系统研究了Ge/Si(001)多层纳米岛材料的快速热退火特性.研究表明:退火过程中纳米岛区的Ge/Si原子互扩散作用比浸润层区强烈;并且随着退火时间增加,这种互扩散作用加大,晶体质量下降,影响材料性能.而在800℃退火12s,材料保持了较小的Ge/Si原子互扩散水平和较高的晶体质量,并且经硼离子注入后的样品在这一条件退火后,超过50%的杂质原子可被激活.     

Ge/Si(001)多层纳米岛材料的快速热退火特性

通过X射线双晶衍射、光致发光谱等手段，系统研究了Ge/Si(001)多层纳米岛材料的快速热退火特性. 研究表明：退火过程中纳米岛区的Ge/Si原子互扩散作用比浸润层区强烈；并且随着退火时间增加，这种互扩散作用加大，晶体质量下降，影响材料性能. 而在800℃退火12s，材料保持了较小的Ge/Si原子互扩散水平和较高的晶体质量，并且经硼离子注入后的样品在这一条件退火后，超过50%的杂质原子可被激活.     

向列型液晶的Raman光谱研究

报道了国产向列型液晶MBBA和EBBA的Raman谱与温度的关系。提出了一种适用于取向的向列型液晶分子振动相关函数和转动相关函数的分离理论。此理论应用于MBBA液晶相和液相的分子振动和转动弛豫的实验研究表明这种分离方法是可行的。     

Si基外延Ge薄膜及退火对其特性的影响研究

采用超高真空化学气相沉积(UHV-CVD)系统,用低温Ge缓冲层技术在Si衬底上外延了张应变Ge薄膜.扫描电镜(TEM)图表明Si基外延Ge薄膜拥有低的位错密度,原子力显微镜(AFM)测试Ge层表面粗糙度仅为1.2 nm.对Si基外延Ge薄膜进行了不同温度下的退火,并用双晶X射线衍射(DCXRD)曲线和Raman谱进行...     

Si1-xGex/Si多层异质外延结构的研究

对制作的Ｓｉ１－ｘＧｅｘ／Ｓｉ多层异质外延结构进行了研究。并对其做了反射高能电子衍射（ＲＨＥＥＤ）、Ｘ射线衍射（ＸＲＤ）和扩展电阻（ＳＲ）等测量，给出了利用这种结构研制出的异质结双极晶体管（ＨＢＴ）的输出特性曲线。     

Ge/Si复合纳米结构电荷存储特性的模拟研究

这一研究工作模拟计算了 Ge/ Si复合纳米结构 MOSFET存储器的擦写和存储时间特性。结果表明 ,Ge/ Si复合纳米结构存储器在低压下即可实现 μs和 ns量级编程。与 Si纳米结构存储器相比 ,由于 Ge/ Si复合势阱的作用 ,器件的电荷保留时间提高了 3～ 5个量级 ,有效地解决了快速擦写编程与长久存储之间的矛盾 ,使器件的性能得到明显改善。     

Ge/Si量子阱结构的C-V特性的模拟

采用有限深对称方势阱近似模型求解薛定谔方程得到Ge/Si量子阱中的子能级分布,并基于迭代法数值求解泊松方程模拟计算了量子阱结构样品在不同偏压下的载流子浓度分布和C-V特性.C-V曲线上电容平台的存在是量子阱结构C-V特性的显著特征,它与量子阱结构参数有密切的关系.随着覆盖层厚度的减小,C-V曲线上平台起始点的电容值增加,并且向低电压方向移动直至其消失.随着量子阱中的掺杂浓度提高,阱中的载流子浓度也会相应增加,那就需要更高的外加电压才能耗尽阱中的载流子,因此平台宽度也就随着掺杂浓度的增加而增加.当覆盖层厚度增加时,由于电压的分压作用,使得降在量子阱上的分压相应减少,因此需要更大的外加偏压才能使阱中载流子浓度全部耗尽,这就使平台的宽度增大.同样地,当覆盖层掺杂浓度增加时,覆盖层中更多的载流子转移到阱内,也就需要更高的外加偏压才能使阱中载流子全部耗尽,平台的宽度也就随之增大.     

Potential of asymmetrical Si/Ge and Ge/Si based hetero-junction transit time devices over homo-junction counterparts for generation of high power

Static and dynamic properties of both complementary n-Ge/p-Si and p-Ge/n-Si hetero-junction Double-Drift IMPATT diodes have been investigated by an advanced and realistic computer simulation technique, developed by the authors, for operation in the Ka-, V- and W-band frequencies. The results are further compared with corresponding Si and Ge homo-junction devices. The study shows high values of device efficiency, such as 23%, 22% and 21.5%, for n-Ge/p-Si IMPATTs at the Ka, V and W bands, respectively. The peak device negative conductances for n-Si/p-Ge and n-Ge/p-Si hetero-junction devices found to be 50.7 ? 10⁶ S/m² and 71.3 ? 10⁶ S/m², which are ～3-4 times better than their Si and Ge counterparts at the V-band. The computed values of RF power-density for n-Ge/p-Si hetero-junction IMPATTs are 1.0 ? 10⁹, 1.1 ? 10⁹ and 1.4 ? 10⁹ W/m², respectively, for Ka-, V- and W-band operation, which can be observed to be the highest when compared with Si, Ge and n-Si/p-Ge devices. Both of the hetero-junctions, especially the n-Ge/p-Si hetero-junction diode, can thus become a superior RF-power generator over a wide range of frequencies. The present study will help the device engineers to choose a suitable material pair for the development of high-power MM-wave IMPATT for applications in the civil and defense-related arena.     

Thermal stability of Si/Gen/Si heterostructures by photoreflectance

The thermal stability of Si/Ge_n/Si(001) heterostructures includingn = 1, 6, 20, and 100 monolayers (ML’s) is studied in connection with their electronic structures through the measurement of photoreflectance (PR). The PR spectra are observed at 90 K over the energy range 0.85–4.0 eV. Comparing the PR signals of Si/Ge _n /Si(001) heterostructures before and after thermal annealing at 600° C, it is found that the samples with less than 6 ML Ge show no change whereas those with more than 20 ML Ge show large changes. The result suggests that Si/Ge _n /Si heterostructures with Ge layer thickness less than 6 ML’s are thermally stable. For the heterostructures with 20 and 100 ML Ge, the relaxation of strain in the Ge layer is found to occur from the PR spectra ofE ₀(Ge),E ₁(Ge) andE ₁ +Δ ₁(Ge), andE ₁(Si).     

Potential of asymmetrical Si/Ge and Ge/Si based hetero-junction transit time devices over homo-junction counterparts for generation of high power

Static and dynamic properties of both complementary n-Ge/p-Si and p-Ge/n-Si hetero-junction Double-Drift IMPATT diodes have been investigated by an advanced and realistic computer simulation technique,developed by the authors,for operation in the Ka-,V- and W-band frequencies.The results are further compared with corresponding Si and Ge homo-junction devices.The study shows high values of device efficiency,such as 23%, 22%and 21.5%,for n-Ge/p-Si IMPATTs at the Ka,V and W bands,respectively.The peak device negative conductances for n-Si/p-Ge and n-Ge/p-Si hetero-junction devices found to be 50.7×10~6 S/m~2 and 71.3×10~6 S/m~2, which are～3-4 times better than their Si and Ge counterparts at the V-band.The computed values of RF power-density for n-Ge/p-Si hetero-junction IMPATTs are 1.0×10~9,1.1×10~9 and 1.4×10~9 W/m~2,respectively,for Ka-,V- and W-band operation,which can be observed to be the highest when compared with Si,Ge and n-Si/p-Ge devices.Both of the hetero-junctions,especially the n-Ge/p-Si hetero-junction diode,can thus become a superior RF-power generator over a wide range of frequencies.The present study will help the device engineers to choose a suitable material pair for the development of high-power MM-wave IMPATT for applications in the civil and defense-related arena.     

Ge/Si量子阱结构的C-V特性的模拟

采用有限深对称方势阱近似模型求解薛定谔方程得到Ge/Si量子阱中的子能级分布,并基于迭代法数值求解泊松方程模拟计算了量子阱结构样品在不同偏压下的载流子浓度分布和C-V特性.C-V曲线上电容平台的存在是量子阱结构C-V特性的显著特征,它与量子阱结构参数有密切的关系.随着覆盖层厚度的减小,C-V曲线上平台起始点的电容值增加,并且向低电压方向移动直至其消失.随着量子阱中的掺杂浓度提高,阱中的载流子浓度也会相应增加,那就需要更高的外加电压才能耗尽阱中的载流子,因此平台宽度也就随着掺杂浓度的增加而增加.当覆盖层厚度增加时,由于电压的分压作用,使得降在量子阱上的分压相应减少,因此需要更大的外加偏压才能使阱中载流子浓度全部耗尽,这就使平台的宽度增大.同样地,当覆盖层掺杂浓度增加时,覆盖层中更多的载流子转移到阱内,也就需要更高的外加偏压才能使阱中载流子全部耗尽,平台的宽度也就随之增大.     

Research and Design of Ge0.6Si0.4／Si Strained—layer Superlattice Planar Optical Waveguide

Calculation shows that the refraction index of Ge0.6Si0.4/Si strained-layer superlattice n≈3.64,when Lw=9 nm and Lb=24 nm.An algorithm of numerical iteration for effective refraction index is emploted to obtain different effective refraction indexes at different thickness(L) .As a result, the thickness of Ge0.6Si0.4/Si strained-layer superlattice optical waveguide,L≤363 nm, can be determlned, which is very important for designing waveguide devices.An optical waveguidecan be madeinto a nanometer device by using Ge0.6Si0.4/Si strained-layer superlattice.