硅p-n结太阳电池对DF激光的响应

对硅p-n结太阳电池在DF激光辐照下的响应进行了理论和实验研究。推导了p-n结反向饱和电流随温度的近似变化关系。根据该近似关系,计算了太阳电池在DF激光辐照过程中输出电压的变化曲线。计算结果和实验结果之间取得了比较好的一致性。     

硅p-n结太阳电池对DF激光的响应

 对硅p-n结太阳电池在DF激光辐照下的响应进行了理论和实验研究。推导了p-n结反向饱和电流随温度的近似变化关系。根据该近似关系，计算了太阳电池在DF激光辐照过程中输出电压的变化曲线。计算结果和实验结果之间取得了比较好的一致性。     

多晶碲化锌薄膜载能子超快动力学实验研究

利用双波长飞秒激光抽运-探测实验方法测量了掺氮多晶ZnTe薄膜在飞秒激光加热情况下载能子超快动力学过程. 采用包含电子弛豫过程和晶格加热过程的理论模型拟合实验数据, 二者符合得很好. 拟合得到10 ps以内影响掺氮多晶ZnTe薄膜表面超快反射率变化的三个弛豫过程的时间常数均为亚皮秒量级. 其中, 正振幅电子弛豫过程是由电子-光子相互作用引起的载流子扩散和带间载流子冷却过程, 负振幅电子弛豫过程是由缺陷造成的光激载能子的俘获效应引起的, 晶格加热过程主要通过电子-声子耦合过程进行的.     

Numerical simulation of the magnetoresistance effect controlled by electric field in p–n junction

The magnetoresistance effect of a p–n junction under an electric field which is introduced by the gate voltage at room temperature is investigated by simulation. As auxiliary models, the Lombardi CVT model and carrier generationrecombination model are introduced into a drift-diffusion transport model and carrier continuity equations. All the equations are discretized by the finite-difference method and the box integration method and then solved by Newton iteration.Taking advantage of those models and methods, an abrupt junction with uniform doping is studied systematically, and the magnetoresistance as a function of doping concentration, SiO_2 thickness and geometrical size is also investigated. The simulation results show that the magnetoresistance(MR) can be controlled substantially by the gate and is dependent on the polarity of the magnetic field.     

Calculation of the Interelectronic-Interaction Correction to Radiative Recombination of an Electron with a Heavy He-Like Ion

We present a calculation of the interelectronic-interaction correction of first order in 1/Z for radiative recombination of an electron with a heavy He-like ion in the ground state. A rigorous relativistic treatment is demonstrated which includes the Coulomb, Breit and retarded parts of the interelectronic interaction. A complete relativistic evaluation is compared with two frequently used approximations. This revised version was published online in July 2006 with corrections to the Cover Date.     

Structural and surface analysis of thin-film ZnTe formed with pulsed-laser deposition

Nanosecond pulses of a Nd:YAG laser have been employed to deposit thin-film zinc telluride (ZnTe) on silicon (Si) and glass without heating these substrates. We present and discuss the structural and surface properties of films deposited at 1064 nm and 532 nm. X-ray diffraction and analysis of the surface roughness with atomic force microscopy reveal that the material texture and surface morphology depend on the ablation laser line used rather than on the substrate. The observations contribute to improved understanding of pulsed-laser deposition and provide tools to optimize the optoelectronic and photonic properties of ZnTe thin-films as well as their incorporation into Si-based technologies in order to fabricate cost-effective and functional optoelectronic devices and all-optical laser digitizer.     

飞秒纳秒脉冲激光微构造和掺杂单晶硅

在SF6气氛下,分别利用钛宝石飞秒脉冲激光与掺钕钇铝石榴石纳秒脉冲激光对单晶硅表面进行了微构造和重掺杂,以用于光伏材料。对制备的单晶硅表面微结构的形貌、结晶性和硫元素杂质含量与分布进行了研究。实验结果表明纳秒脉冲激光制备的单晶硅表面微结构的薄层电阻较小,缺陷密度较低（结晶性高）,硫元素杂质含量较高且在表面分布的范围较广,深度较大（约1 m）。此外,材料的可见-近红外波段吸收率可接近80%。基于纳秒脉冲激光微构造的单晶硅的优异性能,在样品表面制备了有效光照面积达8 cm2的太阳能电池。其中,最佳太阳能电池的串联电阻、开路电压、短路电流密度分别为0.5 , 503 mV, 35 mA/cm2,转换效率约12%。上述太阳能电池性能还可通过优化制备工艺进一步提高。     

Study of the pulsed laser vapor doping of Si(1 0 0) with KrF excimer laser and BCl3 gas

The properties of pulsed laser vapor doping on p-Si(1 0 0) with a KrF (248 nm) excimer pulsed laser (248 nm) and BCl₃ gas are reported in this paper. The doped samples are characterized by the resistance measured using a four-probe method, since the sheet resistance changes with the carrier concentration of the sample. The doping effects with the variation of laser energy density, pulse number, and the pressure of BCl₃ were investigated in terms of the sheet resistance. In this way, the optimized parameters were obtained and used for the positive heavy doping on p-Si(1 0 0) and p-Si(1 1 1). Then, using a square mesh under the above conditions, an image doping was completed. Finally, the metal–semiconductor Ohmic contacts were realized by plating Ag and Cu films on the doped surface.     

The influence of electronic transport across interface junction between Si substrate and the root of ZnO micro-prism on field emission performance

ZnO micro-prisms are prepared on the p-type and n-type Si substrates, separately. The $I$--$V$ curves analysed by AFM show that the interface junctions between the ZnO micro-prisms and the p-type substrate and between the ZnO micro-prisms and the n-type Si substrate exhibit p--n junction behaviour and ohmic contact behaviour, respectively. The formation of the p--n heterojunction and ohmic contact is ascribed to the intrinsic n-type conduction of ZnO material. Better field emission performance (lower onset voltage and larger emission current) is observed from an individual ZnO micro-prism grown on the n-type Si substrate. It is suggested that the n-Si/n-ZnO interfacial ohmic contact benefits the electron emission; while the p-Si/n-ZnO interface heterojunction deteriorates the electron emission.     

Development of ZnTe film with high copper doping efficiency for solar cells

Since a hole barrier was formed in back contact due to mismatch of work function, the back contact material for CdTe cell has been a significant research direction. The ZnTe:Cu is an ideal back contact material, which reduces the valence band discontinuity and can be used as the electron back reflection layer to inhibit interface recombination. The conductivity of ZnTe:Cu film is improved by applying RF-coupled DC sputtering and post-deposition heat treatment. The doping efficiency is computed as the ratio of free hole density and copper concentration, which can be correlated with performance for CdTe-based solar cell. The higher doping efficiency means that more copper atoms substitute for Zn sites in ZnTe lattices and less mobilized copper atoms remain which can enter into the CdTe absorber layer. Copper atoms are suspected as dominant element for CdTe-based cell degradation. After optimizing the ZnTe:Cu films, a systematic study is carried out to incorporate ZnTe:Cu film into CdTe solar cell. The EQE spectrum is kept relatively stable over the long wavelength range without decreasing. It is proved that the conduction band barrier of device with ZnTe:Cu/Au contact material has an effect on the EQE response, which works as free electron barrier and reduces the recombination rate of free carrier. According to the dark J—V data or the light J—V data in the linear region, the current indicates that the intercept gives the diode reverse saturation current. The results of ideality factor indicate that the dominant recombination occurs in the space charge region. In addition, the space charge density and depletion width of solar cell can be estimated by C—V profiling.     

Dependences of spin polarization on the control parameters in the spin-polarized injection through the magnetic p-n junction

Effective spin-polarized injection from magnetic semiconductor (MS) to nonmagnetic semiconductor (NMS) has been highlighted in recent years. In this paper we study theoretically the dependence of nonequilibrium spin polarization (NESP) in NMS during spin-polarized injection through the magnetic p-n junction. Based on the theory in semiconductor physics, a model is established and the boundary conditions are determined in the case of no external spin-polarized injection and low bias. The control parameters that may influence the NESP in NMS are indicated by calculating the distribution of spin polarization. They are the doping concentrations, the equilibrium spin polarization in MS and the bias. The effective spin-polarized injection can be realized more easily by optimizing the above parameters.     

连续激光诱导Zn/InP掺杂过程中温度分布的解析计算

在实验的基础上，分析表面蒸发Zn的InP样品在连续激光诱导下掺杂Zn过程.在一维热传导问题的第三类边界条件下，给出激光辐照有限厚双层材料Zn/InP温度分布的一种直观简洁的解析形式. 关键词： 激光诱导掺杂 Zn/InP 温度分布     

Tailoring electronic and transport properties of edge-terminated armchair graphene by defect formation and N/B doping

First principle calculations based on Density Functional Theory and nonequilibrium Green's function methods were carried out on a p-n junction device made of armchair graphene nanoribbons (GNR), with B and N doping and with defects, to examine transport properties of these systems. Doping and defects were found to lower band gap compared to pristine GNR. N-doping leads to the smallest band gap and the highest current (17.18 μA at 0.9 V bias, −12.82 μA at −1 V bias). B-doping shows the least current. Extensive delocalisation in N-doped system suggests a strong coupling between p and n parts, making the system a high rectifying diode. Linear correspondence between transmission coefficient and projected density of states suggest robust negative differential resistance effect. Tuning of efficiency of such p-n junction by doping and defect suggests the design of suitable nanoelectronic devices in future.     

Calculation of the characteristics of radiative multiphoton absorption and emission lines when an atom interacts with pulsed laser radiation

We have used the quantum electrodynamic theory of moments and the S-matrix formalism of Gell-Mann and Low to carry out numerical modeling of the characteristics (shift, width) of radiative multiphoton absorption lines for an atom in the field of a multimodal laser pulse with gaussian and soliton-like shapes. We have studied the effect of multimode character on the characteristics of multiphoton resonances, using as an example the 6S-6F transition in the cesium atom at the wavelength 1059 nm. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 2, pp. 271–274, March–April, 2007.     

新型缓冲层分区电场调制横向双扩散超结功率器件

为了突破传统横向双扩散金属-氧化物-半导体器件(lateral double-diffused MOSFET)击穿电压与比导通电阻的极限关系,本文在缓冲层横向双扩散超结功率器件(super junction LDMOS-SJ LDMOS)结构基础上,提出了具有缓冲层分区新型SJ-LDMOS结构.新结构利用电场调制效应将分区缓冲层产生的电场峰引入超结(super junction)表面而优化了SJ-LDMOS的表面电场分布,缓解了横向LDMOS器件由于受纵向电场影响使横向电场分布不均匀、横向单位耐压量低的问题.利用仿真分析软件ISE分析表明,优化条件下,当缓冲层分区为3时,提出的缓冲层分区SJ-LDMOS表面电场最优,击穿电压达到饱和时较一般LDMOS结构提高了50%左右,较缓冲层SJ-LDMOS结构提高了32%左右,横向单位耐压量达到18.48 V/μm.击穿电压为382 V的缓冲层分区SJ-LDMOS,比导通电阻为25.6 mΩ·cm2,突破了一般LDMOS击穿电压为254 V时比导通电阻为71.8 mΩ·cm2的极限关系.     

Improvement of the thermoelectric efficiency of pyrene-based molecular junction with doping engineering

In this study, the thermoelectric properties of pyrene molecule doped with boron and nitrogen atom at different sites of molecule are investigated using density functional theory and none-equilibrium Green's function formalism in the linear response regime. Our calculations show that when the impurities are added to the edge of the molecule, the anti-resonant peaks will appear in the transmission diagram in the vicinity of the Fermi energy level. So it increases the thermoelectric figure of merit of the system in comparison with the one that the impurity is located in the center of molecule. Additionally,the seebeck coefficient signs are not the same among the B, N, and N B doped devices, indicating that the types of the carriers can be changed with different types of doping.     

基于择优掺杂取向研究Y掺杂量对ZnTe电子结构和吸收光谱的影响

Zn Te由于其特有的禁带宽度,光学性质以及可重掺杂等特性,使得众多学者对其进行了系列的相关研究,但关于Y掺杂浓度和掺杂方式对Zn Te性质的影响却鲜有报道.作者采用密度泛函理论框架下的广义梯度近似方法,分别计算了Y在掺杂浓度为1.56at%、3.12at%、4.69at%下Zn Te的几何结构、能带结构、态密度分布、吸收光谱等性质,以及不同掺杂方式对体系的影响.结果表明:在掺杂浓度为3.12at%,掺杂方式不相同时,掺杂原子沿[111]晶向排布的形成能最低,即[111]晶向为择优晶向.当掺杂浓度为4.69at%时,择优晶面为(111)面.若要实现更高浓度的Y掺杂,沿(111)晶面掺杂更容易实现.对于实验而言,更高浓度的Y掺杂,掺杂原子在Zn Te体系中更容易沿(111)晶面进行集中排列. Y掺杂Zn Te后,体系的禁带宽度变大,吸收光谱发生蓝移,对可见光的吸收强度减小.在浓度为3.12at%时禁带宽度最大,蓝移现象最明显,吸收强度最小. Y掺杂后体系变为n型半导体,可以使用这种掺杂方式制作P-N结二极管．     

Metal surface coloration by oxide periodic structures formed with nanosecond laser pulses

In this work, we studied a method of laser-induced coloration of metals, where small-scale spatially periodic structures play a key role in the process of color formation. The formation of such structures on a surface of AISI 304 stainless steel was demonstrated for the 1.06 µm fiber laser with nanosecond duration of pulses and random (elliptical) polarization. The color of the surface depends on the period, height and orientation of periodic surface structures. Adjustment of the polarization of the laser radiation or change of laser incidence angle can be used to control the orientation of the structures. The formation of markings that change their color under the different viewing angles becomes possible. The potential application of the method is metal product protection against falsification.     

Production of antihydrogen by recombination of \barp with e+: What can we learn from electron--ion collision studies?

Basic relations relevant to the observation of radiative recombination are presented and experiments on both spontaneous and laser-stimulated recombination of ions with free electrons are reviewed. In particular, the observation of unexpected high spontaneous recombination rates at very low energies is discussed. The fundamental and applied interest in the observed rate enhancement effects has recently triggered new experimental and theoretical work which can provide new insight into the problem of direct recombination of antiprotons with positrons to form antihydrogen. This revised version was published online in August 2006 with corrections to the Cover Date.