量子阱带间跃迁探测器基础研究（特邀）

在最近的实验中,PN结型量子阱结构被观察到反常的载流子输运情况,其相应的物理机制和载流子输运模型被提出。通过系统实验观察到,PN结量子阱结构材料在共振激发模式下,仍可测出开路电压或短路电流。对比开路和短路情况下的光致荧光（PL）光谱,发现短路下PL强度明显降低。这说明短路状态下的光生载流子没有被限制在量子阱内,而是逃逸出结区。这种载流子逃出量子阱的现象却没有在等量偏压下的NN型量子阱结构中发现,说明载流子逃出量子阱并非由传统的热激发或隧穿的作用导致。据此,笔者提出了相应的物理机制和载流子输运模型对此现象进行解释,认为光生载流子能在PN结内建电场的作用下直接逃出量子阱,并且辐射复合发光发生在载流子逃逸过程之后。     

基于石墨烯的肖特基结辐射伏特同位素电池

从传统肖特基结辐射伏特同位素电池金属电极存在的对放射源衰变粒子的阻挡及导电性不理想的问题出发,借鉴石墨烯肖特基结太阳电池结构,将石墨烯/硅肖特基结引入辐射伏特同位素电池中,在63Ni放射源的照射下验证石墨烯/硅肖特基结换能单元在辐射伏特同位素电池中应用的可行性.研究结果发现,基于硝酸掺杂,当少层(3?5层)石墨烯经过4...     

GaAs基辐射福特效应电池电极图案设计

研究了串并联电阻对太阳能电池和β伏特效应电池的影响, 并在此基础上提出了GaAs基β伏特效应电池的电极图案设计原则。在该原则的指导下设计了一批GaAs基PIN结的电极图案,测试了这些PIN结在⁶³Ni源辐照下的输出特性。与传统的梳状电极相比,本文电极设计可以降低对⁶³Ni辐射β粒子的反散射和阻挡作用,有效的增加了电池的输出电流,而这种电极设计不会对电池的开路电压,填充因子和理想因子带来不利的影响。     

中科院电工所制备铁电—半导体耦合光伏器件

正据《中国科学报》报道,经中国科学院太阳光伏发电系统和风力发电系统质量检测中心认证,中国科学院电工研究所化合物薄膜太H能电池研究组在普通钠钙玻璃上制备的铁电半导体耦合光伏器件的转化效率为11.3%。铁电半导体耦合光伏器件又称纳米偶极子太阳能电池,属于第三代太阳能电池。与传统PN结不同,该器件通过具有铁电特性的纳米颗粒矩阵的极化电场产生内建电场,并由填充在纳米偶极子颗粒之间的半导体介质充当吸光材料的     

基于电致发光成像理论的硅太阳电池缺陷检测

基于半导体电致发光（EL）的基本理论,在理想P-N结模型条件下,定量计算正向偏压时硅太阳电池EL强度与少数载流子扩散长度的对应关系;分析了电池片中缺陷和扩散长度（EL强度）的关系,指出通过硅电池EL图像检测电池缺陷的可行性。搭建实验平台,分别拍摄单晶硅和多晶硅电池的EL图像,从中成功检测出各种缺陷;编写可视化裂纹自动检...     

利用半导体PN结模型分析石英玻璃的极化过程

利用半导体PN结偏置过程的理论模型,类比分析了玻璃的热及电场极化过程。理论分析表明,在热及电场极化条件下,正、负电极与玻璃分界面处的电场及电荷分布规律与其在反向、正向偏置的2个PN结处非常相似;利用PN结偏置模型,并考虑玻璃极化过程中电子的作用,修正了极化玻璃中电场分布和载流子运动方程及其边界条件,并解释了一些已有实验现象。     

半导体器件物理量的测定

一、引言 扫描电子显微镜的电子束感生电流技术广泛地用于测量半导体的物理量。本文主要介绍利用这种电子束感生电流信息确定PN结的位置,测量平面器件PN结的结深,测量半导体表面载流子的复合速度,确定材料局部区域少数载流子的扩散长度和寿命,测量PN结的耗尽区宽度,研究PN结耗尽区宽度与偏置电压的关系。由于它是一种近年来最新的技术,其原理是基于电子束与固体的相互作用,这种相互作用过程直接反应了半导体的结构和特性,因而可以用它进行半导体材料研究,半导体器件新机理的研究,表面科学的研究以及半导体器件可靠性的研究。为推广这种技术的应用,提高半导体器件水平,我们向读者介绍一下这种电子束技术,报告我们的研究成果。     

一维均匀掺杂突变PN结伽马剂量率辐射解析模型

研究硅基半导体集成电路最基本结构之一PN结的伽马剂量率辐射模型,阐明PN剂量率辐射模型的重要意义。根据半导体物理基本方程,推导计算出在剂量率辐射下一维均匀掺杂突变PN结光电流响应的解析解模型,根据解析解,在不同参数下用Mathematica作图观察,并与计算机辅助设计技术(TCAD)数值模拟仿真结果对比,验证解析解的正确性;最后基于解析解,通过分析剂量率、偏压、PN结几何尺寸、掺杂浓度、载流子扩散系数、少子寿命等参数对稳态光电流的影响,提出一个更方便工程计算的稳态光电流模型。     

应用于CdTe太阳能电池热离子发射与扩散理论

该文运用了载流子的热离子发射理论与扩散理论来分析类型II异质结CdTe薄膜太能电池的载流子输运过程,得到了一个综合而全面的载流子电流电压输运方程;由该输运方程可知,对于窄准中性区的CdTe太能电池,流过其结的总电流由热离子发射过程来制约;反之,则由扩散过程来限制结的总电流。对于基于类型II异质结的薄膜太阳能电池,该输运方程可以为其更深入的研究,如各类掺杂情况边界条件的确定、转换效率的计算等,提供很好的理论基础。     

基于结模型的极化石英光纤内建电场分析

用多载流子模型分析了D型石英光纤的热极化过程及耗尽层的形成,分析了氢离子注入及钠离子耗尽层的形成.并把正负电荷的交界处类比为pn结,分别计算了所形成的内建电场大小.最终得出极化完成后石英光纤的二阶非线性效应主要由钠离子的耗尽形成,计算出的内建电场大小约为108 V/m,由此算出的二阶非线性系数的数值在0.10～0.60 pm/V,和实验报道数值符合较好.     

Built-in electric field thickness design for betavoltaic batteries

Isotope source energy deposition along the thickness direction of a semiconductor is calculated,based upon which an ideal short current is evaluated for betavoltaic batteries.Electron-hole pair recombination and drifting length in a PN junction built-in electric field are extracted by comparing the measured short currents with the ideal short currents.A built-in electric field thickness design principle is proposed for betavoltaic batteries:after measuring the energy deposition depth and the carrier drift length,the shorter one should then be chosen as the built-in electric field thickness.If the energy deposition depth is much larger than the carrier drift length,a multi-junction is preferred in betavoltaic batteries and the number of the junctions should be the value of the deposition depth divided by the drift length.     

Electrode pattern design for GaAs betavoltaic batteries

The sensitivities of betavoltaic batteries and photovoltaic batteries to series and parallel resistance are studied.Based on the study,an electrode pattern design principle of GaAs betavoltaic batteries is proposed.GaAs PIN junctions with and without the proposed electrode pattern are fabricated and measured under the illumination of ⁶³Ni.Results show that the proposed electrode can reduce the backscattering and shadowing for the beta particles from ⁶³Ni to increase the GaAs betavoltaic battery short circuit currents effectively but has little impact on the fill factors and ideal factors.     

Design and analysis of permanent magnet-type bearingless motors

Magnetic bearings have been applied to high speed and high power electric machines for machine tools, turbomolecular pumps, etc. Bearingless motors can be expected to realize high speed and high power ratings because magnetic bearing functions are integrated into high-speed motors, which results in a simplified structure with short shaft length. In this paper, permanent magnet type bearingless motors, having built-in capability to achieve high power factor and high efficiency, are proposed. The shaft is suspended and centered by electromagnetic forces produced by currents in the additional radial force windings of the stator slots. At first the relationships of these radial forces, currents and voltages are derived analytically. Moreover, the relationships between radial forces and permanent magnet thickness are found. The optimal permanent magnet thickness is determined. The ratio of radial force over current as well as the peak air-gap flux density are discussed. These relationships are confirmed by prototype machines     

Effect of lateral transport of photoinduced charge carriers in a heterostructure with a two-dimensional electron gas

It is shown that the nonequilibrium charge carriers produced by a local optical disturbance of the heterostructure with a two-dimensional electron gas are transported in the plane of the structure over an extremely large distance from the excitation location, which greatly exceeds the diffusion length in the bulk. The effect is attributable to the fact that the photogenerated electrons and holes are separated by the built-in electric field of the heterojunction to opposite edges of the buffer layer, where they are transported along parallel planes. The distance over which the nonequilibrium carrier density spreads reaches large values because of 1) the high conductivity of two-dimensional electrons, 2) the barrier for electron-hole recombination, and 3) hole drift in the electric field produced by the charge of nonequilibrium carriers in the plane of the structure. Fiz. Tekh. Poluprovodn. 31, 393–399 (April 1997)     

Electron transport and ionization in silicon at high fields

The saturated drift velocity measured for electrons at high fields is inconsistent with Shockley's model for impact ionization in silicon. It is explained in terms of a field-dependent mean free path for high energy phonon creation in the electric field direction, electrons creating a high energy phonon as soon as they have acquired sufficient energy from the field. Assuming that the electron wavepacket travels at the saturated drift velocity without dispersion, it can be shown that the increased scattering rate at high fields must result in a large spread in the carrier energy. If a drifted Maxwellian distribution is assumed, a unique expression can be obtained for the carrier temperature T^* which is in good agreement with the measured field dependence of the ionization coefficient. In this model, a cylindrical hot carrier distribution must be assumed with the hot carrier energy in a plane perpendicular to the applied field. Exact calculations of the magneto-resistance of such a distribution can be made verifying that the drift velocity is indeed saturated.     

CdTe p—i—n薄膜太阳能电池热平衡态数值分析

通过应用Ｓｃｈａｒｆｅｔｔｅｒ－Ｇｕｍｍｅｌ解法数值求解Ｐｏｉｓｓｏｎ方程，对热平衡态ｐ（ＺｎＴｅ）／ｉ（ＣｄＴｅ）／ｎ（ＣｄＳ）薄膜太阳能电池进行计算机数值模拟。结果表明，ｐ（ＺｎＴｅ）／ｉ（ＣｄＴｅ）／ｎ（ＣｄＳ）的能带结构有利于光生载流子传输与收集，ＣｄＴｅ中高内建场提高了光生载流子通过有源区的输运能力，对ＣｄＴｅ进行适量Ｐ型掺杂还能提高其电池的短波收集效率。     

非晶硒对X射线响应特性的理论研究

较为全面地考查了非昌硒对Ｘ射线的灵敏度。引入一个灵敏度模型，在灵敏度与载流子迁移特性、光子能量、非晶硒厚度和场强之间建立了明确的关系。计算结果表明，载流子迁移长度至少应是非晶硒厚度的２倍以上，才能使Ｘ射线激发的电子、空穴有较大的概率到达收集电极（或非晶硒自由表面）（即信号收集效率）；用加大非晶硒厚度的方法增加灵敏度时必须考虑信号收集效率降低的负面影响；场强对灵敏度有重要影响，提高场强可使非晶硒灵敏     

A novel high voltage LIGBT with an n-region in p-substrate

A novel 4μm thickness drift region lateral insulated gate bipolar transistor with a floating n-region(NRLIGBT) in p-substrate is proposed.Due to the field modulation from the n-region,the vertical blocking capability is enhanced and the breakdown voltage is improved significantly.Low area cost,high current capability and short turn-off time are achieved because of the high average electric field per micron.Simulation results show that the blocking capability of the new LIGBT increases by about 58%when compared with the conventional LIGBT (C-LIGBT) for the same 100μm drift region length.Furthermore,the turn-off time is shorter than that of the conventional LIGBT for nearly same blocking capability.     

Origin of high fill factor in polymer solar cells from semiconducting polymer with moderate charge carrier mobility

The fill factor of polymer bulk heterojunction solar cells (PSCs), which is mainly governed by the processes of charge carrier generation, recombination, transport and extraction, and the competition between them in the device, is one of the most important parameters that determine the power conversion efficiency of the device. We show that the fill factor of PSCs based on thieno[3,4-b]-thiophene/benzodithiophene (PTB7):[6,6]-phenyl C₇₁-butyric acid methylester (PC₇₁BM) blend that only have moderate carrier mobilities for hole and electron transport, can be enhanced to 76% by reducing the thickness of the photoactive layer. A drift–diffusion simulation study showed that reduced charge recombination loss is mainly responsible for the improvement of FF, as a result of manipulating spatial distribution of charge carrier in the photoactive layer. Furthermore, the reduction of the active layer thickness also leads to enhanced built-in electric field across the active layer, therefore can facilitate efficient charge carrier transport and extraction. Finally, the dependence of FF on charge carrier mobility and transport balance is also investigated theoretically, revealing that an ultrahigh FF of 80–82% is feasible if the charge mobility is high enough (∼10⁻³–10⁻¹ cm²/V s).