重掺杂硅物理参数的低温特性分析

本文考虑了杂质重掺杂引起的禁带变窄效应，提出了新的电离率和有效多数载流子浓度的数学模型，并应用于由发射效率决定的硅双极晶体管电流增益的计算，所获得的计算结果与实验相符合，这为硅低温半导体器件的设计提出了理论基础。     

多晶硅发射极晶体管的低温频率特性研究

本文考虑低温下半导体中载流子冻析效应和浅能级杂质的陷阱效应等因素，分析了多晶硅发射极晶体管的低温频率特性，研究表明，受载流子冻析效应的影响，基区电阻在低温下随温度下降接近于指数上升，使晶体管的频率性能变坏；而由于浅能级杂质的陷阱效应，低温下基区和发射区渡越时间变长，截止频率下降，这些因素在低温器件设计中应予重视。     

低温多晶硅发射极晶体管电流增益和截止频率的解析模型

本文综合考虑了多晶硅发射极的载流子输运障碍,界面氧化物遂穿、晶粒间界杂质分凝和界面能带弯曲等因素,以及禁带变窄效应、低温下载流子冻析效应和浅能能补偿杂质隐阱效应,建立了低温多晶硅发射极晶体管电流增益和截止频率的解析模型,对电流增益和截止频率的温度关系进行了理论分析并与３００Ｋ和７７Ｋ下的实测结果进行了比较。     

多晶硅发射极晶体管的低温频率特性研究

本文考虑低温下半导体中载流子冻析效应和浅能级杂质的陷阱效应等因素,分析了多晶硅发射极晶体管的低温频率特性。研究表明,受载流子冻析效应的影响,基区电阻在低温下随温度下降接近于指数上升,使晶体管的频率性能变环;而由于浅能级杂质的陷阱效应,低温下基区和发射区渡越时间变长,截止频率下降。这些因素在低温器件设计中应予重视。     

黑硅薄膜的电学输运特性

采用飞秒激光在六氟化硫气氛中对硅表面进行扫描,在硅衬底上制备了具有超饱和硫重掺杂的黑硅薄膜。采用变温霍尔测试方法,在30~300 K温度范围内测试了黑硅薄膜-硅衬底双层结构的载流子浓度温度特性和迁移率温度特性。采用双层结构的霍尔载流子浓度模型和霍尔迁移率模型,从测试结果中分离出黑硅薄膜的载流子浓度温度特性和迁移率温度特性。采用杂质带电离载流子模型拟合黑硅薄膜的载流子浓度温度特性,得到黑硅薄膜的硫杂质带的中心能级为Eds=-159 meV,高斯半高宽为50.57 meV,有效硫浓度Nds=1.0cm-3×1020cm-3,室温下硫的电离率为7%。计算得到的杂质带态密度分布图,此时杂质带与导带开始融合,黑硅薄膜发生了绝缘体金属转化现象,并解释了黑硅薄膜载流子浓度温度特性中随温度升高激活能增大的现象。黑硅薄膜载流子迁移率特性说明,在低温下杂质散射是主要的散射机制,在高温下声子散射是主要的散射机制。并采用硅中载流子迁移率的经验模型,将黑硅薄膜载流子迁移率分离成导带电导和杂质带电导两部分,得到杂质带的迁移率μi在1~10 cm2/Vs。     

4H-SiC中点缺陷的第一性原理研究

基于密度泛函理论和第一性原理,对4H-SiC晶格中5种点缺陷(VC,VC-C,填隙B,替位B和替位P)的晶格常数、电荷布居、能带等微观电子结构进行了计算,并从缺陷形成能、杂质电离能和载流子浓度等角度分析了这些点缺陷对材料性能的影响.计算结果表明:在这些点缺陷中,C空位的形成能最低,仅为5.929 1 eV,属于比较容易形成的一类点缺陷.同时在能带图中可以看到填隙B的禁带中央附近出现了一条新能带,这条新能带的产生促使填隙B成为5种缺陷中禁带宽度最小的缺陷,有利于SiC半导体器件中载流子的输运.在3种杂质点缺陷中,替位P的电离能最小.掺杂杂质电离能越小,电离程度越深,产生的载流子浓度也越大,这一结论在载流子浓度的计算结果中也得到了验证.     

SiGe-HBT中雪崩击穿效应对电流电压特性的影响

本文报道了一个在较宽温度范围内能精确描述6H SiC JEFT性能(包括亚阈区)的器件模型，器件的电流电压特性由包含少数几个物理模型参数连续统一的解析表达式表述.该模型也包括了串联电阻效应、沟道中电子速度饱和效应、饱和区的有限输出电导、温度决定的模型参数等效应.载流子的计算考虑了SiC中杂质能级特点，采用两级电离模型，模拟了典型结构器件的高温特性，结果和实验符合很好.     

强电场中铯原子双光子光电离光谱研究

报道了对铯原子在双光子激发条件下的强电场光电离光谱进行实验研究的结果。发现钩原子较大量子亏损导致的核心效应可影响到场电离阈值以上的光谱特性，但对零场阈值附近强场共振特性的影响可以忽略。     

用红外光吸收方法测定Hg_(1-x)Cd_xTe中电离杂质浓度和微沉淀物

由于动量守恒和能量守恒的要求,固体中自由载流子的光吸收过程总是伴随着声子或电离杂质散射过程。声子和电离杂质散射的强度很大程度上决定了自由载流子吸收系数。对于像Hg_(1-x)Cd_xTe这样的极性混晶半导体,采用唐文国的双模Callen有效电荷就可以计算出光学声子的散射强度,对于给定的样品,它仅和温度有关。声学声子和无序散射都微乎     

低温硅双极晶体管电流增益研究

着重分析了多晶硅发射极对提高电流增益的作用和低温下集电区中性杂质碰撞电离引起的电流倍增效应，导出多晶硅发射极晶体管电流增益的表达式，很好地解释了实验结果。     

杂质非完全离化对SiC n-MOSFET电特性的影响

文章研究了SiC中杂质非完全离化对器件性能的影响.通过考虑场致离化效应,分析了空间电荷区电荷密度与表面势的关系,得出在SiC MOSFET反型条件下,可近似认为杂质完全离化.在此基础上,模拟了4H-SiC MOSFET的漏电流-栅压曲线和迁移率-栅压曲线.模拟结果与实验数据非常吻合.     

Ionization energy of copper in Hg0.8Cd0.2Te crystals under conditions of light and intermediate doping

Resistivity and the Hall effect were studied in copper-doped p-Hg _0.8 Cd _0.2 Te crystals in the temperature range of 4.2–125 K and the range of Cu concentrations from 2.6×10¹⁵ to 2×10¹⁸ cm^?3. It is shown that the conventional method for determining the ionization energy of impurities from the slope of the dependence R _H (T) is inapplicable in this case. In order to obtain the correct results, it is necessary to take into account the structure of the impurity band and the screening of the impurity charge with free charge carriers. A simplified model of the impurity band is suggested; this model makes it possible to calculate the ionization energy of acceptors under conditions of light doping and a small degree of compensation. This approach is used to find that ionization energy of copper depends only slightly on the copper concentration at T=0 and is equal to E _A =7.6 meV for an isolated acceptor, which coincides with the theoretical value. At finite temperatures, the ionization energy of acceptors decreases appreciably as a result of screening.     

Charge-sheet model for silicon carbide inversion layers

The charge-sheet model for metal-oxide-semiconductor (MOS) inversion layers is extended to silicon carbide. The generalized model is based on an analytical solution of the Poisson equation for the case of incomplete ionization of dopant impurities and incorporating Fermi-Dirac statistics. The results are compared with the conventional charge-sheet model which assumes complete impurity ionization and nondegenerate statistics. It is found that, at room temperature and for gate voltages in weak and moderate inversion, the present model predicts higher inversion-layer charge density at a given gate voltage. However, the relationship between the inversion charge and the surface Fermi potential is essentially independent of the degree of impurity ionization. In strong inversion or at temperatures above ~600 K, the differences between the two models are small. A formula is given for the threshold voltage as a function of the impurity ionization energy. The effects of several different interface state energy distributions on inversion charge are investigated. It is found that a slowly-varying interface-state density has an effect on threshold voltage of a MOSFET similar to that of a fixed oxide charge, while an interface-state density that increases at least exponentially with energy has the effect of lowering the field-effect mobility and transconductance     

Admittance spectroscopy: A powerful characterization technique for semiconductor crystals—Application to ZnTe

The admittance spectroscopy technique is shown to be a very convenient tool for analyzing majority carrier traps: energy level, capture cross section and concentrations are easily obtained without complicated mathematical treatment. The series resistance in the material underlying the Schottky or pn junction is also detected when the free carriers are freezing out. It allows to get the shallowest level energy and its compensation ratio. The method has been applied to ZnTe material analysis and the effect on the admittance of six different acceptors is demonstrated. When comparing the electrically determined ionization energy of a given impurity with its optical value the former appears as systematically lower but most of the difference can be ascribed to Poole Frenkel or impurity concentration effects.     

Incomplete ionization in a semiconductor and its implications to device modeling

The ionization of impurity atoms is an important process in determining the number of free carriers, and thus the conductivity and other physical properties, in semiconductors. In this paper, a detailed derivation for the ionization percentage of impurity atoms is given. Furthermore, to illustrate the errors associated with the conventional complete ionization assumption, the results are applied to the modeling of the current–voltage characteristics of a p/n junction diode. Two-dimensional device simulations are included in support of the model.     

基于摄动法研究短沟道SOI MOSFET亚阈值特性

提出了一种新的方法对短沟道SOI MOSFETs亚阈区的二维表面势的解析模型进行了改进,即摄动法.由于在短沟道SOI MOSFETs中不仅需要计及不可动的电离杂质,而且需要考虑自由载流子的数量和分布的影响.利用摄动法求解非线性泊松方程可以得到短沟道SOI MOSFETs二维的表面势解析模型.通过与二维数值模拟器MEDICI模拟结果比较,证明了在亚阈区改进模型所得的结果比只计及不可动的电离杂质的SOI MOSFETs模型所得的结果吻合更好.     

超晶格中浅杂质能带与光吸收

超晶格BEST模式像传感器是近几年来发展的非常有潜力的红外探测器件。本文结合这种器件计算和讨论了超晶格中浅杂质能谱和光吸收,给出了:杂质能带;杂质离化能;杂质能带的带宽和能态密度;杂质基态与第一束缚子能带基态间光跃迁:量子化极限尺寸以及其它性质。这不但具有一定物理意义,并对于BEST模式红外传感器件的光吸收有一定参考价值。     

Excess gate current analysis of junction gate FET's by two- dimensional computer simulation

Gate current in a JFET under high drain bias is much higher than expected from the classical theory for reverse-biased p-n junctions. This excess gate current is caused by minority carriers generated by low-level impact ionization in the conducting channel, while the so-called breakdown voltage is determined by high-level avalanche multiplication near the gate edge at the surface. A simple one-dimensional model for the excess gate current is proposed. This model is based on the results of two-dimensional numerical analysis, which neglects the minority carrier motion. The excess gate current and avalanche breakdown voltage are calculated from one-dimensional ionization integrals, which are obtained numerically by utilizing the solution of two-dimensional analysis. The reverberant effect of the generated carriers on the potential distribution is assumed to be negligible. The results of the calculation are in good agreement with experimental results, without any adjustable parameters. Moreover, various impurity doping profiles are analyzed for the purpose of minimizing excess gate current. The present model requires a reasonably short computation time and is useful for designing JFET devices.     

Physical Principles of Self-Consistent Simulation of the Generation of Interface States and the Transport of Hot Charge Carriers in Field-Effect Transistors Based on Metal–Oxide–Semiconductor Structures

A detailed simulation of degradation (caused by hot charge carriers) based on self-consistent consideration of the transport of charge carriers and the generation of defects at the SiO₂/Si interface is carried out for the first time. The model is tested using degradation data obtained with decananometer n-type-channel field-effect transistors. It is shown that the mutual influence of the above aspects is significant and their independent simulation gives rise to considerable quantitative errors. In calculations of the energy distribution for charge carriers, the actual band structure of silicon and such mechanisms as impact ionization, scattering at an ionized impurity, and also electron–phonon and electron–electron interactions are taken into account. At the microscopic level, the generation of defects is considered as the superposition of single-particle and multiparticle mechanisms of breakage of the Si–H bond. A very important applied aspect of this study is the fact that our model makes it possible to reliably assess the operating lifetime of a transistor subjected to the effects of “hot” charge carriers.