硼掺杂球磨SiGe合金的热电性能

SiGe合金热电材料作为一种传统的高温热电材料一直以来受到广泛关注。本研究通过B在球磨SiGe合金中的P型掺杂,有效增加了材料的载流子浓度,优化材料的电学性能。通过球磨降低材料的晶粒尺寸,增强晶界对声子的散射,降低材料的晶格热导率。另外,B掺杂使点缺陷散射和载流子-声子散射得到增强,材料的晶格热导率进一步降低。在室温时,Si_(0.8)Ge_(0.2)B_(0.04)的晶格热导率为~4Wm~(-1) K~(-1)。由于掺杂后电导率提高,热导率降低,因此热电优值zT得到了提高。在850K时,Si_(0.8)Ge_(0.2)B_(0.04)的最大热电优值为0.42,与Si_(0.8)Ge_(0.2)B_(0.002)的样品相比,其优值提高了2.5倍左右。     

改善放大器噪声性能的SiGe HBT几何参数优化设计

研究有源器件SiGe HBT的几何参数对单片低噪声放大器(LNA)噪声性能的影响.基于0.35μm SiGeBiCMOS工艺,研制了4款采用不同几何参数的SiGe HBT LNA.实验结果显示,在给定的偏置条件下,当发射极宽长比较小时,小范围改变发射极宽度对噪声系数(NF)改善微弱,但适当增长发射极条长和增加发射极条数明显降低了NF,且不牺牲增益.另外,与采用其他几何尺寸的SiGe HBT LNAs相比,选用器件发射极面积为AE=4μm×40μm×4的LNA性能最优,在0.2～1.2 GHz内获得低至2.7 dB的噪声系数,高达26.7 dB的相关增益和最接近于50Ω的最佳噪声源阻抗.由于没有使用占片面积大的电感,放大器芯片面积仅为0.2 mm2.     

SiGe／Si和SGOI材料的Li离子束RBS分析

SiGe合金薄膜中的Ge含量度分布对材料的禁带宽度和制作器件的性能有十分重要的影响。本文用Li离子束卢瑟福背散射分析法对SiGe／Si和SiGe-OI材料样品进行了分析。与TEM，SEM、Raman等分析结果进行比较表明，Li离子束RBS分析可同时测量SiGe层厚度，Ge含量度其深度分布，Si过渡层和SiO2层厚度，并有较好的测量精度。     

Power·delay product in COSMOS logic circuits

In this simulation work, we use COSMOS logic devices—a novel single gate CMOS architecture recently announced [1]—in multi-input logic gates, assessing its performance in terms of power·delay product. We consider three different multi-input logic circuits: a two-input NOR gate, a three-input NOR gate, and a three-input composite NOR/NAND (NORAND) gate. For this power·delay analysis, the transient TCAD simulations are employed in a mixed-mode approach where circuit and device simulations are coupled together, culminating in the delay response of the circuits as well as the static/dynamic current components. The analysis shows that all circuits, except the 3-input NOR gate, has acceptable characteristics at low-power applications and static leakage limits all COSMOS circuits at high-bias conditions.     

太赫兹Si/SiGe量子级联激光器的能带设计

使用nextnano3模拟软件计算Si/Si1-xGex/Si量子阱的能带结构,对Si/SiGe量子级联激光器有源区的能带结构进行设计,结果表明使用Ge组分为0.27～0.3,量子阱宽度为3nm的SiGe合金与垒宽为3nm的Si层构成对称应变级联异质结构,有利于优化THz Si/SiGe量子级联激光器结构.     

高频大功率SiGe/Si HBT的设计

详细地阐述了高频大功率SiGe/Si异质结双极晶体管(HBT)设计中的一些主要问题,主要包括器件的纵向设计中发射区、基区以及收集区中掺杂浓度、形貌分布、层厚的选择以及横向布局设计中的条宽、间隔的选择等.并对这些主要参数的选择给出了一些实用的建议.     

多发射极Si/SiGe异质结晶体管

在硅衬底上外延生长一层Si_(1-x)Ge_x合金材料,它的带隙随组分x的增加而变窄,如果用Si_(1-x)Ge_x窄带材料作晶体管基区,利用硅作为集电极和发射极构成双极晶体管,就可以很容易实现器件的高频、高速、大功率。设计了一种以Si/Si_(1-x)Ge_x/Si为纵向结构,梳状10指发射区为横向结构的异质结晶体管,利用双台面工艺方法制造出具有如下参数的器件:电流增益β=26、V_(CB)=7V、I_(CM)≥180mA、f_T≤ 2GHz,实现了高频大功率,充分显示出Si/Si_(1-x)Ge_x材料的优越性。     

Photoreflectance Spectroscopy for Study of Si/SiGe/Si Heterostructure

UHVCVD-grown Si/Si1- xGex/Si heterostructure was investigated by Photoreflectance spectroscopy (PR). The principle of PR used in semiconductor film was thoroughly described. According to the E1 transition energy in the Si1- xGex alloy, the Ge content in SiGe film with constant composition can be accurately characterized. In this study, determine the composition uniformity of larger diameter SiGe epiwafer by PR mapping technique was determined. These results show PR is very promising for Si1- xGex epilayer characterization with constant Ge content and can provide film measurements for production-worthy line monitor.     

Effect of Ion Dose on Growth of Relaxed SiGe Layer on Ion Implantation Si Substrate

Thin strain-relaxed Si0.8Ge0.2 films (57.6 nm) on the 30 keV Ar ion implantation Si substrates for different dose (1 × 1014, 5 × 1014, 3 × 1015 cm-2) were grown by ultra high vacuum chemical vapor deposition (UHVCVD) system.Rutherford backscattering/ion channeling (RBS/C), high resolution X-ray diffraction (HRXRD), Raman spectra as well as atomic force microscopy (AFM) were used to characterize these SiGe films. Investigations by RBS/C as well as HRXRD demonstrate that these thin Sio.8Geo.2 films could indeed epitaxially grow on the Ar ion implantation Si substrates. Under low dose ( 1 × 1014 cm-2) and medium dose (5 × 1014 cm-2) implantation conditions, the relaxation extents of SiGe films are 60.6% and 63.6%, respectively. However, high dose implantation (3 × 1015 cm-2) prompt the strain in epitaxial SiGe film to be close to full relaxation status (relaxation extent of 96.6% ). On the other hand, determinations of RBS/C also indicate the crystalline quality of SiGe film grown on high dose implantation Si substrate is nearly identical to that grown on low dose (1 × 1014 cm-2) implantation Si substrate.     

Mechanism of anomalous recovery in advanced SiGe bipolar transistors after low dose rate irradiation for very high total doses

The possible physical mechanism of the anomalous recovery effect in SiGe bipolar transistors is described. The qualitative analysis of saturated oxide trapped charge and interface trap densities at very high total doses as a function of dose rate affords an explain of decreasing excess base current and increasing current gain during further low dose rate irradiation.