基于结模型的极化石英玻璃内建电场分析

用多载流子模型分析玻璃的热极化过程及其内部耗尽层的形成,极化电场的作用使载流子在玻璃内的迁移及由外界的注入最终形成交替的电荷分布,形成类似两个相向p-n结的结构。针对几种典型的p-n结电荷分布形式,计算了相应内建电场及二阶非线性极化率,极化完成后产生的宏观非线性效应主要由钠离子耗尽形成的突变结电场(~3′109V/m)决定,二阶非线性极化率的数值在0.2~1.2pm/V之间,耗尽区分布在阳极表面下25mm的范围。     

具有组分梯度的HgCdTe探测器光电特性

PN结分别制备在HgCdTe外延薄膜材料的Cd组分非线性分布区和线性分布区的高组分端,研究了具有组分梯度的HgCdTe探测器的光电特性。计算不同温度下组分梯度产生的内建电场,结果显示Cd组分线性分布产生的内建电场在100～200 V/cm,而Cd组分非线性分布使得样品表面薄层的内建电场高达2 000 V/cm,推测组分梯度产生的内建电场对光生少子运动的影响是引起两个样品光电性能差异的主要原因。通过分析样品响应率随温度的三种不同变化趋势,提出利用温度调控组分梯度产生的内建电场,有利于降低空间电荷效应,为大注入下提高HgCdTe探测器的饱和阈值提供了一种新的设计思路。     

聚合物偶极子天线型光纤电场传感器

设计并初步成功制作了聚合物光纤电场传感器.假设聚合物材料的电光系数r13=10 pm/V,设计的两种电场传感器的半波电场Eπ=36.2和15.8 kV/m.用自制的二阶非线性光学聚合物BPAN-NT作为聚合物光纤电场传感器的芯层材料,制作了电光调制器.用反应离子刻蚀的方法制作脊形光波导,通过电晕极化使芯层具有电光效应,...     

Si中场致光整流效应的研究

通过观测Si/Al肖特基势垒受光照时产生的光生电压与光波偏振方向和晶向的变化关系,发现了光生电压的各向异性规律,即光敏面不同点处光敏特性不同,并且有一定规律.经理论分析和实验数据曲线拟和,认为这是由于金属和半导体接触形成势垒,产生内建电场,电场的存在使晶体对称性被破坏,产生二阶非线性效应的光整流,光整流产生的直流电场又与内建电场相互作用的结果.     

熔融石英的热及电场诱导机理

详细分析了熔融石英样品经热及电场诱导后 ,建立二阶极化率的机理。该机理表明 ,二阶极化率是由样品耗尽区中偶极子的定向和三阶极化率经强静电场作用共同形成的。在一般条件下诱导 ,前者是主要因素 ;在较高电压诱导时 ,后者是主要因素。推导了二阶极化率的表达式 ,并进行了数值计算。数值结果表明 ,在一般情况下 ,χ3 3 ( 2 ) 约 1pm/V ,χ3 3 ( 2 ) ∶χ3 1( 2 ) 约为 3。理论证明提高诱导的外加电压和选用Na和OH杂质浓度较大的石英材料能提高二阶极化率。     

石英光纤二阶非线性效应初探

首先讨论和比较了两种不同诱导石英光纤的方案，即掺杂物和／或光诱导方案及电场诱导方案，分析了它们各自的特点，在此基础上提出了一种新的诱导方法。预期新方法诱导出石英光纤的二阶非线性系数可与ＬｉＮｂＯ３的二阶非线性系数ｄ３１相比拟。     

用于电力工程的光纤电压电场传感器

本文叙述了光纤电压电场传感器的结构和性能。在工频电压60～6000V和工频电场强度50～5000V/cm 条件下验证了这种光纤电压电场传感器, 其非线性误差小于1%,信噪比达1000。     

内建电场对应变多量子阱带阶的影响

隧穿电流的大小依赖于带阶的大小.内建电场会改变多量子阱的结构,使其由方阱变为斜阱,导致其带阶发生改变.本文定量地给出了由内建电场导致的价带阶变化及其斜率.对沿任意方向生长的立方超晶格系统,当其特征厚度小于临界值(欠临界系统)时,给出了内建电场与应变的定量关系.针对不同的量子阱系统,当生长方向沿着[111]方向时,计算了三种类型、21种组分、由内建电场引起的价带阶变化量.所有结果在线性领域及没有相变的情况下都是适用的.     

有强内电场的GaN-基阶梯量子阱中的线性与非线性光吸收

采用密度矩阵方法,考察了带强内建电场GaN-基阶梯量子阱中的线性与非线性光吸收系数.基于能量依赖的有效质量方法,在考虑了带的非抛物性情况下,推导了结构中的精确解析的电子本征态,给出了系统中简单解析的线性与非线性光吸收系数表达式.以AlN/GaN/AlxGa1-xN/AlN阶梯量子阱为例进行了数值计算.结果发现阶梯量子阱的阱宽Lw、阶梯垒宽Lb、阶梯垒的掺杂浓度x的减小将提高体系的吸收系数.而且,随着Lw,Lb和x减小,吸收光子的能量有明显的蓝移,总吸收系数的半宽度及饱和吸收强度均减小.计算获得的部分结果与最近的实验观察完全一致.     

内建电场对应变多量子阱带阶的影响

隧穿电流的大小依赖于带阶的大小。内建电场会改变多量子阱的结构 ,使其由方阱变为斜阱 ,导致其带阶发生改变。本文定量地给出了由内建电场导致的价带阶变化及其斜率。对沿任意方向生长的立方超晶格系统 ,当其特征厚度小于临界值 (欠临界系统 )时 ,给出了内建电场与应变的定量关系。针对不同的量子阱系统 ,当生长方向沿着 [111]方向时 ,计算了三种类型、2 1种组分、由内建电场引起的价带阶变化量。所有结果在线性领域及没有相变的情况下都是适用的。     

Simple model for space-charge region capacitance of an exponential-constant p-n junction

Depletion layer properties have been calculated for an exponential-constant p-n junction in silicon by using a simple model. Closed-form expressions are presented for the built-in voltage V/sub bi/ and the offset voltage correction Delta V, respectively, for this junction. These formulas allow the depletion capacitance to be accurately determined from a given value of applied voltage V/sub a/ by manual calculations. The results obtained can readily be extended to other semiconductor materials and other diffused p-n junctions.<>     

Analysis and capacitive measurement of the built-in-field parameter in highly doped emitters

An elementary theory of a strongly asymmetric n⁺-n-p junction, assuming an exponential tail of the donor concentration profile in the depletion layer, is presented and supported by numerical computations. The drastic effect of the built-in field upon the minority carrier flow is discussed. A detailed expression of the static capacitance is then derived and shown to lead to an improved measurement of theC(V)law, capable of yielding the internal field parameter around the edge of the depletion layer in the emitter. Typical experimental results are reported and discussed.     

Electron holography study for two-dimensional dopant profile measurement with specimens prepared by backside ion milling

The visualization of two-dimensional dopant profiles and the quantitative analysis of the built-in potential across the p-n junction, DeltaV(p-n), by electron holography were carried out with specimens prepared from the backside ion milling method combined with the focused ion beam technique. It was possible to obtain dopant profiling of the large field of view with low surface damage and gradually changed thickness. From the quantitative analysis using the phase information of electron holography and the thickness information of electron energy-loss spectroscopy, DeltaV(p-n) was estimated to be about 0.78 V assuming that the thickness of the dead layer on both surfaces is 50 nm, which is to show the difference of within 12% from the calculated value. It demonstrates that the backside ion milling method is a very promising specimen preparation technique for the reliable and quantitative analysis of dopant profiling with electron holography.     

Analysis of persistent photoconductivity due to potential barriers

Persistent photoconductivity has been seen in thin silicon resistors fabricated with SIMOX material at temperatures between 60 and 220 K. This effect has been attributed to the depletion of carriers near the interface between the top silicon layer and the buried oxide, which is due to the large number of surface traps at this interface. The depletion of carriers is accompanied by a built-in field on the order of 10,000 V/cm, which causes a potential barrier that is nearly a quarter of the energy gap of silicon. The theory of the recombination kinetics of majority carriers with minority carriers trapped at the interface on the other side of a potential barrier is studied. Both the possibilities of tunneling and thermal activation have been considered. The results show that thermal activation dominates at the temperatures of our measurements in SIMOX material, while at lower temperatures tunneling would dominate.     

阳极连接中碱金属双离子迁移模型􀀂

在假设玻璃中仅有两种可动碱金属离子的情况下，提出了一个金属－玻璃电场辅助阳极连接模型。根据该模型，玻璃中的Na和K耗尽层厚度在演化过程中成比例，它们的演化规律决定于耗尽层边上的负电荷层。数据拟合结果表明，文献[4]中的Na、K耗尽层厚度与连接时间的关系可用时间的对数函数很好地描述。K富集层起因于K^ 离子的中和，Na耗尽导上的负电荷产生的电场引起了实验中测得K^ 离子跃迁激活能与Na^ 离子的激活能几乎相等。阳极连接过程中不存在稳态，总可观测到微小电流，该电流仍源于离子电导。     

The tunneling P-N junction

The tunneling probability in an Esaki diode is very much dependent on the electric field strength which is itself dependent on the local fluctuations of ion concentration. The fluctuation of depletion layer thickness due to randomness of ion position is calculated. It is shown that most of the tunneling current is carried by only a small fraction of the total area.     

Quantum model of electron accumulation at charged boundaries of heavily doped semiconductor films

A new quantum model of electron accumulation at positively charged boundaries of semiconductor films has been developed. It is based on the well-known concepts of quantum confinement of transverse electron motion in a uniform electric field, the role of which is played by the effective field of attraction to positive surface donor centers. Electrons with a surface density equal to the donor concentration occupy the corresponding quasi-discrete states according to the Fermi statistics. At reasonable concentrations all the electrons of the accumulation layer are mainly concentrated at the first quantum-confinement level. Ultra-high built-in fields on the order of the atomic level (10⁸ V/cm) correspond to the onset of filling the third level. The potential profile, which describes the interaction of the accumulation-layer electrons with other charged particles (including holes) is calculated by double integration of the Poisson equation with the electron density in the form of squares of the corresponding segments of the Airy function. Its boundary value—the surface potential—describes the effect of the electron-accumulation layer on the external electric circuit. The obtained dependence of the surface potential on the resulting boundary electric field (including that induced by the built-in charge) is easily transformed into the corresponding capacitance-voltage characteristics.     

On approaches to the built-in electric-field calculations in shallow silicon n+-p junctions

A critical appraisal of recent approaches to the built-in electric-field E calculations in shallow heavily doped strongly asymmetric silicon n⁺-p junctions is performed. The existence of a large (≃ 1 - V/µm), positive field E of built-in nature on the surface of the n⁺-layer-reported previously through the computation of E as a gradient of erfc impurity profile in very steep n⁺-p junctions-is refuted on the grounds of semiconductor fundamentals. Alternatively, it is shown that: 1) under thermal equilibrium conditions and a "free" (air or vacuum) silicon surface, the built-in field should necessarily go to zero at the semiconductor surface; 2) if the projected built-in field E nears the surface on the heavily doped side of a junction, then it is compulsory to take into account the interaction between E and the prevailing surface charges. The results of this work suggest that all processes in the surface-controlled region of the heavily doped layer are being shaped by the interplay of the bulk field E created by the impurity gradients with the field Esurforiginated in the surface states.