Surface Barrier Models of ZnO

For a low surface barrier, the energy band, barrier height and width of the space charge region at the surface of relatively large grains of ZnO are presented analytically on condition that the electron distribution obeys the Boltzmann statistics. It is shown that the temperature in the space charge distribution factor has an important effect on the energy band, barrier height and width of the space charge region. The depletion approximation is a model in which the temperature in the space charge distribution factor is zero. Our results are better than the depletion approximation.     

A model for shifts in the gate turn-on voltage of insulated-gate field-effect devices induced by ionizing radiation

Insulated gate field-effect devices with thermally grown silicon dioxide and deposited nitride insulation were subjected to electron irradiation up to a total dose of sufficient magnitude to establish dynamic equilibrium. The resultant linear shift of the gate turn-on voltage with applied gate bias over a wide range of biasing conditions has been interpreted by a model postulating a positive space charge region bounded by the insulator-semiconductor interface and a negative space charge region bounded by the insulator-metal interface. It is shown that the linearity holds for an arbitrary space charge distribution within these two regions whose widths are independent of the gate voltage during irradiation. The conditions for obtaining completely radiation-resistant devices have also been derived.     

Temperature dependence of turn-on voltage of gold-doped MOSFETs

The temperature dependence of the turn-on voltage of gold-doped and control n- and p-channel MOSFETs has been measured. To account for the large positive shift of turn-on voltage, VT Au, of gold treated n- and p-channel devices, it has been proposed that the gold eliminates the fast interface traps of continuous energy distribution, and that additional acceptor states very close to the valence band can cause additional charge QA Au, which can dominate the effect of acceptor and donor levels of gold ions in the silicon surface space charge region, and can also over-compensate the surface state charge, Qss. To fit the theoretical VT Auversus T curve to experimental curves, an accumulation of electrically active gold within the surface space charge region has been considered in n-channel devices and depletion in p-channel devices.     

基于有效态密度的MOS结构电荷控制模型

从载流子在 MOS结构反型层内的分布出发 ,利用表面有效态密度 ( SLEDOS:SurfaceLayer Effective Density- of- States)的概念 ,在经典理论框架内建立了包含载流子分布对表面势影响的电荷控制模型 .该模型包含了强反型区表面电势的变化对载流子浓度的影响 ,采用了一种新的高效的迭代方法 ,具有较高的计算效率和足够的精度要求     

Surface traps-related nonvolatile resistive switching memory effect in a single SnO2:Sm nanowire

For nanostructure SnO2,it is very difficult for its electric properties to accurately control due to the presence of abundant surface states.The introduction of Sm can improve the traps in surface space charge region of SnO2 nanowires,resulting in a controllable storage charge effect.For the single nanowire-based two-terminal device,two surface state-related back-to-back diodes are formed.At a relatively large voltage,electrons can be injected into the traps in surface space charge region from negative electrode,resulting in a decrease of surface barrier connected with negative electrode,and contrarily electrons can be extracted from the traps in surface space charge region into positive electrode,resulting in an increase of surface barrier connected with positive electrode.The reversible injection and extraction induce a nonvolatile resistive switching memory effect.     

The effect of the minority carrier distribution on the threshold voltage of a MOSFET

Based upon the concept of minority carrier transverse diffusion within the surface space charge region and its resultant quasi-Fermi level distribution, a simple one-dimensional theory of the threshold voltage for both long- and short-channel MOSFETs is developed. In the new model, the non-uniform distribution of the quasi-Fermi level for minority carriers with respect to that for majority carriers is characterized by introducing an effective diffusion length and is averaged over all the channel length. The non-uniformity in the quasi-Fermi level for minority carriers results in a non-uniform bulk charge density which is averaged similarly. Using the above averaged values and considering the charge-sharing effect, the threshold voltage for a MOSFET is expressed. Numerical results are obtained which show the strong dependence of threshold voltage on the effective diffusion length, which can not be overlooked especially when the device is scaled down. The theoretical calculations are also compared to the experimental data for the fabricated NMOS and PMOS. The good agreement supports the correctness of the developed theory.     

一种新的MOS结构量子化效应修正模型

从载流子在 MOS结构反型层内的经典分布和量子化后的子带结构出发 ,提出了经典的和量子化的表面有效态密度 (SL EDOS:Surface layer effective density- of- states)的概念。利用表面有效态密度的概念建立了经典理论框架和量子力学框架内的电荷分布模型。该模型包含了强反型区表面电势的变化对载流子浓度的影响 ,具有很高的计算效率和稳定性。在模型基础上 ,研究了量子化效应对反型层载流子浓度和表面电势的影响。     

磁控管中的空间电荷效应研究

对磁控管中由于外加磁场存在而导致的空间电荷效应进行了研究.通过求解正交场中的粒子运动方程,给出了阴极表面电位分布与外加磁场和阴极发射电流的关系,并指出磁控管中合适的发射电流是其最佳工作的前提.通过全电磁粒子仿真和实验测试证实了该效应对磁控管工作性能的影响,为高效率低噪声磁控管的研究提供了新思路.     

Potential probing of a thyristor cross-cut during turn-on

On a cross-cut of a thyristor with a particularly wide n-base, the dynamic change in voltage at the surface was probed during turn-on. Furthermore, the infrared recombination radiation emitted from the regions of carrier storage was observed time-resolved. The results show that during the turn-on delay phase, the load current flows in a channel that widens significantly from the n-emitter towards the p-emitter. Compensation of the stationary charge in the space charge region by free electrons results in a movement of the space charge region towards the p-emitter. Concurrently, the particular distribution of electrons causes the region of maximum fieldstrength to move away from the junction.     

Distribution of the electric field in high-resistivity MSM structures illuminated by nonmonochromatic light

The sensitivity of the electric field distribution to the spectrum of the incident radiation in highly biased, high-resistivity, semiconductor structures of the MSM (metal-semiconductor-metal) type illuminated by nonmonochromatic light is investigated theoretically. It is shown that in the presence of deep impurity levels the field distribution depends strongly on the spectral composition of the incident light. The frequency interval corresponding to optical thicknesses of the order of unity is found to significantly influence the space charge in the bulk of the structure and the electric field distribution E(x), even when the fraction of energy in this region of the spectrum relative to the total flux is extremely minimal. The trapping of holes by a deep impurity level in the bulk of the structure forms a positive space charge and produces qualitatively new field distributions, which increase near the dark electrode with a positive curvature of the function E(x). The impurity trapping of electrons near the illuminated anode imparts a negative space charge to the impurity levels. This phenomenon induces a substantial increase of the field in the electrode sheath and forms in the vicinity of the anode a region wherein the field varies only slightly. All the prominent features disclosed by the calculations in the electric field distributions are observed in experiment. Fiz. Tekh. Poluprovodn. 33, 815–823 (July 1999)     

腐蚀法研究掺Er熔融石英玻璃的真空热极化

掺Er熔融石英片经过真空热极化后，利用40%的HF腐蚀其沿极化电场方向的剖面，通过原子力显微镜（AFM）观测到剖面阳极边极化区内出现了峰-谷-峰形式的形貌变化，研究表明其原因是正负带电离子层的不同腐蚀速度，从而得出极化区内离子层分布为负-正-负的形式，与多载流子模型对真空热极化的解释相一致；根据离子层的分布，采用双高斯模型模拟出极化区内电场分布，并得到与结果相当吻合的理论Maker条纹。     

HBT空间电荷区复合电流的解析模型

建立了异质结双极晶体管ＥＢ结空间电荷区复合电流的解析模型,基于该模型计算出了不同基区掺杂浓度下空间电荷区的复合率,获得了空间电荷区复合电流随外加电压的变化关系。     

A two-dimensional analysis of gallium arsenide junction field effect transistors with long and short channels

A two-dimensional analysis of gallium arsenide junction field effect transistors with long and short gates is presented. The short gate device is shown to have a negative resistance region at low drain voltages which is absent in the long gate device. The negative resistance region depends on the shape of the conducting channel and the distribution of the electron charge. A field dependent mobility is used, and its effect on current saturation is discussed. The electrostatic charge distribution and electric field distribution are calculated for both devices, and are shown in graphic form.     

A two-dimensional analysis of indium phosphide junction field effect transistors with long and short channels

A two-dimensional analysis of indium phosphide junction field effect transistors with long and short gates is presented. The two devices are shown to have properties similar to those of gallium arsenide JFETs. The short gate device has a negative resistance region at low drain voltages which is absent in the long gate device. The negative resistance region is determined by the distribution of the drift velocity along the conducting channel, and the resulting distribution of the electron charge. A field dependent mobility is used, and its effect on current saturation is discussed. The electrostatic charge distribution and electric field distribution are calculated for both devices, and are shown in graphic form.     

Capacitance of MOS diodes on substrates doped non-uniformly near the surface

The usual assumption of uniform doping in the space charge region no longer holds if the doping near the semiconductor surface is changed appreciably by thermal oxidation and/or ion implantation. Poisson's equation becomes the non-linear, but can be solved using suitable approximations for the dependence on the voltage. Thus the exact form of the doping profile is taken into account.The C?V curves of MOS diodes differ considerably from those for uniform doping due to the altered relation between the surface potential and the total charge of the semiconductors as well as due to the altered width of the space charge region. These two contributions are reduced to additive terms if the space charge region covers completely the region with altered doping.For weak depletion the slope of the C?V curves is larger for pile-down of acceptors and pile-up of donors in p-type silicon. The slope becomes smaller for increasing depletion, because the space charge region spreads now to more heavily doped regions of the semiconductor. For pile-up of donors and pile-down of acceptors in n-type silicon, the curves are initially less declined and become steeper according to the smaller doping in the bulk of the semiconductor.     

Calculation of the electrical capacitance of a truncated cone

The paper presents a method for the evaluation of the capacitance and charge distribution of a metallic truncated cone of finite length with top and bottom circular flat plates and isolated in free space, the integral equations relating the potential and unknown charge distribution on the surfaces are solved using the moment method employing pulse and delta functions as basis function and testing functions, respectively. The elements of the matrix to be inverted are found by dividing the surfaces into subsections which are combination of curvilinear rectangles and triangles. Capacitance and charge distribution are evaluated as a function of the geometrical parameters of the structure, numerical results on capacitance and charge distribution are presented     

瞬态C-V方法对Al_xGa_(1-x)As中DX中心的研究

本文指出DX中心电容测量中边区的重要性,提出一种新的瞬态C-V方法,可以用来测量DX中心浓度、导带电子浓度和边区的空间电荷分布及导带电子浓度随温度的变化关系,并由此导出测量DX中心热电离能的方法。另外,还对DX中心正∪和负∪两种模型的理论分析和实验结果进行了比较,得出不同模型所应满足的附加条件。     

Distribution of recombination currents in the space charge regionof heterostructure bipolar devices

This paper addresses the problem of the space charge region Shockley-Read-Hall (SRH) recombination currents in heterojunctions with one noncrystalline side. A formulation which generalizes previous works is discussed. The approach is based on the drift-diffusion model with a thermionic-field emission boundary condition. The main physical parameters which determine the relative contribution of each zone of the space charge region (SCR) to the total recombination current are identified. The general analysis is applied for the first time to amorphous/crystalline heterojunctions and design criteria are established to minimize the total recombination current     

Fermi level pinning by interface states: A calculation of the height and the shape of the Schottky barrier

A calculation of the potential distribution of the space charge region of a metal-semiconductor contact is proposed, which is based on the theories of Schottky and Bardeen. Inspired by the defect model of Spicer et al., we assume that interface states are spread over several atomic layers inside the semiconductor. Thus the “neutral level” of Bardeen can be reached at the most buried states. Particular attention is paid to conditions for which such Fermi level pinning is possible.