Radial junction silicon solar cells with micro-pillar array and planar electrode interface for improved photon management and carrier extraction

We demonstrate radial p-n junction silicon solar cells with micro-pillar array with higher short-circuit current and open-circuit voltage than comparable planar silicon solar cells. Micro-pillar array, fabricated by RIE, acts as an effective anti-reflection coating for visible light with less than 6% reflection. Compared to devices with planar surface, devices with micro-pillar array show a 27% enhancement in short circuit current. The radial p-n junction of the micro-pillars also improves extraction probability of the photogenerated carriers, which further increases the short circuit current. Typically, micro-pillar solar cells suffer from high recombination losses at the Si/metal interface, resulting in poor V_OC. Our devices prevent these recombination losses by planarizing the Si/metal interface, leading to an open circuit voltage of 622?mV, the highest ever reported for micro-pillar solar cells. This planarized contact also reduces the series resistance associated with radial junctions, leading to series resistance of ≤0.50?Ω-cm² and fill factors up to 76.7%.     

Study of Schottky contact in HgCdTe infrared photovoltaic detectors

The changed polarity of transient photovoltage (TPA) from negative to positive induced by ultra fast lasers illumination is studied in the HgCdTe p-n junction photovoltage detector. The negative photovoltaic-response decrease obviously and even disappear by blocking the laser beam with an aperture to limit the illumination area of the linear array detectors. This new phenomenon can be explained by a combined theoretical model of p-n junction and Schottky contact. Using the TPA technique and the combined model, the characters of p-n junction and Schottky contact will be distinguished. Therefore, it could be used in characterizing the Ohmic contact of the detectors electrodes, and its sensitivity is expected to be much higher than the steady states methods.     

点接触放大器的放大作用

For an n-type transistor, with copper and phosphor-bronze whiskers respectively for its emitter and collector, as the result of electrical forming, the emitter should have a metal-p-n structure. In the first part of this paper, the forward characteristics of such a structure is analized for the whole range of current, with special reference to the variation of the emission ratio γ with the current. The design requirement of a flat γ-I_e curve is discussed. The second part of the paper contains an analysis of current amplification of the collector. The structure assumed is a metal-p-n junction, the diffusion of phosphorus into the structure causing a high barrier for holes at the metal contact. By combining the result of the two parts, a resultant a-I_e, relation is calculated for a typical case. The main factors affecting the performance of the transistor and means of its improvement are discussed in some detail.     

Excess mechanical stress induced in mesa p-n junctions by hydrostatic pressure

We consider the excess mechanical stresses induced in semiconductor devices when an external pressure is applied near a p-n junction. The excess stresses are calculated for a p-n tunnel diode under hydrostatic pressure. It is found that these stresses significantly influence the pressure dependence of the peak current in GaAs tunnel diodes. The hysteresis in the peak current is caused by a displacement of electrode material in the neighborhood of the contact.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 60–63, April, 1976.     

Photothermal and photoacoustic effects in semiconductors and semiconductor structures

A theory of photothermal and photoacoustic effects is developed, on which the contactless diagnostics of semiconductors and semiconductor structures are based. Photothermal and photoacoustic effects are characterized quantitatively by the variable temperature of the specimen surface being exposed and by its shift. These quantities are computed in this paper for a homogeneous semiconductor and a semiconductor with a p-n junction with electron transfer processes, heat liberation as a result of thermalization and charge carrier recombination and their passage through the potential barrier as well as nonthermal deformation mechanisms due to nonequilibrium carrier interaction with the lattice in terms of the deformation potential and the reverse piezoeffect taken into account. It is shown that the surface temperature and shift (particularly the phase of these responses) carry information about such semiconductor characteristics as the charge carrier lifetime, the surface recombination rate, the deformation potential constants, the depth of p-n junction location, the height of its potential barrier, etc.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 119–131, June, 1987.     

Graphene/Ag2ZnSnSe4诱导p-n结薄膜太阳电池数值模拟

银锌锡硒(Ag2ZnSnSe4)是一种禁带宽度为1.4 eV的n型半导体材料.本文提出一种由n型Ag2ZnSnSe4与石墨烯(Graphene)组成的Graphene/Ag2ZnSnSe4诱导p-n结薄膜太阳电池,并借助wxAMPS软件对电池的物理机理和性能影响因素进行模拟研究.模拟结果表明,高功函数的石墨烯与n型Ag2ZnSnSe4半导体接触时,Ag2ZnSnSe4吸收层的前端能带向上弯曲,在n型Ag2ZnSnSe4吸收层表面诱导形成p型Ag2ZnSnSe4反型层,p型Ag2ZnSnSe4和n型Ag2ZnSnSe4组成p-n同质结.模拟发现石墨烯和背接触的功函数会影响载流子的分离、输运和收集,严重影响器件性能,石墨烯功函数达到5.5 eV,背接触功函数不高于4.4 eV,都有利于提高器件性能.Ag2ZnSnSe4吸收层的掺杂浓度主要影响器件的短路电流,而Ag2ZnSnSe4吸收层的体内缺陷对器件整体性能产生影响.在石墨烯和背接触功函数分别为5.5和3.8 eV,Ag2ZnSnSe4吸收层的掺杂浓度和缺陷密度分别为1016和1014 cm–3时,Graphene/Ag2ZnSnSe4诱导p-n结薄膜太阳电池能够取得高达23.42%的效率.这些模拟结果为设计新型高效低成本太阳电池提供了思路和物理阐释.     

Determination of the deposition depth of a p-n junction with an electronic probe

A method for determining the deposition depth of a p-n junction is described, which uses comparison of calculated and experimentally measured dependence of short circuit induced current on the energy of bombarding electrons. A formula for induced current is derived with consideration of recombination on the irradiated surface. Calculations are performed to permit study of the character of the short circuit induced current as a function of electron energy in structures with different recombination parameters and different p-n junction deposition depths.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 16–20, August, 1973.     

Investigation of laterally single-diffused metal oxide semiconductor (LSMOS) field effect transistor

We propose a distinct approach to implement a laterally single diffused metal-oxide-semiconductor (LSMOS) FET with only one impurity doped p-n junction. In the LSMOS, a single p-n junction is first created using lateral dopant diffusion. The channel is formed in the p region of the p-n junction and the n region acts as the drift region. Two distinct metals of different work function are used to form the “n⁺” source/drain regions and “p⁺” body contact using the charge plasma concept. We demonstrate that the LSMOS is similar in performance to a laterally double diffused metal-oxide-semiconductor (LDMOS) although it has only one impurity doped p-n junction. The LSMOS exhibits a breakdown voltage of ∼50.0 V, an average ON-resistance of 48.7 mΩ-mm² and a peak transconductance of 53.6 μS/μm similar to that of a comparable LDMOS.     

Electrochemical fabrication of a novel conducting polythiophene film junction

A compact conductive polythiophene (PT) film junction was prepared by potential controlled electrochemical doping after electropolymerization of thiophene. The polythiophene film was cation-doped on one side, while its other side was anion-doped, which resulted in a polythiophene p-n junction film diode. The free-standing polythiophene film junction diode was flexible and was 1.5 times stronger than aluminum metal. After treatment by a strong electric field, the polythiophene p-n junction exhibits a novel electric property like an intelligent electric switch.     

A comparison of barrier type tunnel junction and point contact tunnel junction formed on the same highT c material

By making a combination of both point contact and barrier type tunnel junctions on a single sample of the highT _c superconductor BSCCO (2212) single crystal, we have shown that as the tunneling tip is slowly retracted from the surface a point contact junction gradually evolves from a N-S short to a high resistance tunnel junction. The scaled dynamic conductance (dI/dV) of this point contact tunnel junction becomes almost identical to that of a conventional barrier type tunnel junction and both show a linear dI/dV —V curve. The observation implies that at high resistance a point contact junction behaves in the same way as a barrier type tunnel junction. We suggested that the almost linear tunneling conductance obtained in both the cases most likely arises due to an intrinsic characteristic of the surface of the crystal comprising of a mosaic of superconducting regions of the order of a few nanometers. We also conclude that the barrierless (N-S) point contact obtained by piercing the surface oxide layer of the crystal shows Andreev reflection which we suggest as the origin of the zero bias anomaly often observed in point contact junctions.     

穿透型V形坑对GaN基p-i-n结构紫外探测器反向漏电的影响

研究了GaN基p-i-n（p-AlGaN/i-GaN/n-GaN）结构紫外探测器的漏电机理．实验发现,在位错密度几乎相同的情况下,基于表面有较高密度的V形坑缺陷材料制备的器件表现出较高的反向漏电．进一步的SEM测试发现,这种V形坑穿透到有源区i-GaN、甚至n-GaN层．在制备p-AlGaN电极时,许多金属会落在V形坑中,从而与i-GaN形成了肖特基接触,有些甚至直接和n-GaN形成欧姆接触．正是由于并联的肖特基接触和欧姆接触的存在导致了漏电的增加． 关键词： GaN 紫外探测器 V形坑 反向漏电     

关于p-n合金结中少数载流者的注射理论

本文用一维模型计算了p-n合金结中少数载流者的一般注射理论。这里假设复合率是与注入载流者的密度成正比。首先,我们讨论了大注射和小注射的两种极端情况,这样得到的结果被用作零级近似解来计算p-n结中注入少数载流者的分布情况。用逐步近似的方法我们得到了注射效率和注射强度(即注入少数载流者的密度与原有多数载流者的密度之比)间的解析关系。在同样的基础上也得到了通过结的总电流密度和注射强度间的类似关系。这理论的结果表明;对一个平常的合金结晶体三极管来说,当发射极电流增加时,发射极的注射效率逐渐下降。在很大的注射强度下,注射效率趋近于极限值1/(1+b),其中b是电子迁移率与空穴迁移率之比。对一个具有很低注射效率的p-n合金结来说,在注射电流小的时候,注射效率是正比于通过结的总电流;当往射电流很大时,注射效率趋近于极限值1/(1+b)。理论结果还表明,在小注射情下,通过p-n合金结的总电流是正比于注射强度;而在大注射情况下,它是正比于注射强度的平方。     

Interplay of conductance, force, and structural change in metallic point contacts

The coupling between two atomically sharp nanocontacts provides tunable access to a fundamental underlying interaction: the formation of the bond between two atoms as they are brought into contact. Here we report a detailed experimental and theoretical analysis of the relation between the chemical force and the tunneling current during bond formation in atom-scale metallic junctions and their dependence on distance, junction structure, and material. We found that the short-range force as well as the conductance in two prototypical metal junctions depend exponentially on the distance and that they have essentially the same exponents. In the transition regime between tunneling and point contact, large short-range forces generate structural relaxations which are concomitant with modifications of the surface electronic structure and the collapse of the tunneling barrier.     

Characterization of Schottky barrier diodes fabricated from electrochemical oxidation of α phase brass

By careful selection of chloride ion concentration in aqueous sodium chloride, electrochemical oxidation of α phase brass is shown to permit fabrication of either p-type copper (I) oxide/metal or n-type zinc oxide/metal Schottky barrier diodes. X-ray photoelectron and Auger electron spectroscopies provide evidence that barrier formation and rectifying qualities depend on the relative surface abundance of copper (I) oxide and zinc oxide. X-ray diffraction of the resulting diodes shows polycrystalline oxides embedded in amorphous oxidation products that have a lower relative abundance than the diode forming oxide. Conventional I/V characteristics of these diodes show good rectifying qualities. When neither of the oxides dominate, the semiconductor/metal junction displays an absence of rectification.     

Determining the height of potential barriers in metal — dielectric — metal tunnel structures by the method of derivatives of the volt — ampere characteristics

The problem is considered here of determining, by an experimental method, the height of potential barriers in metal — dielectric — metal tunnel structures at the junctions. Formulas are derived according to which one can calculate the height of a potential barrier from measurements of the first and the second derivative of the tunnel current with respect to the bias voltage across a junction.     

有机硅化合物-金属氧化物绝缘保护材料在制造高压晶闸管中的应用研究

采用高纯有机硅化合物和金属氧化物,按比例均匀混合制成糊状材料,涂敷于器件台表面,用于半导体p-n结表面特性的控制和保护.固化后该材料在室温下的体电阻率大于7.5×10¹⁵Ω·cm,介电常数为4.7,击穿电压高于16 kV/mm.该材料用于KP500型晶闸管表面保护,能明显改善器件的表面特性、减少漏电流和提高耐压水平,并对提高器件性能的机理进行了研究. 关键词： 绝缘保护材料 性能 晶闸管 机理     

p-n结二极管结区边界附近的交流电特性

基于p-n结二极管的理想工作状态的基本假定,推导了二极管在交流电下工作时其基区和p-n结分界面附近上的时间常数与二极管空间尺寸、扩散长度、载流子寿命和外加交流电频率等的依赖关系.结果发现高频和低频两种状态下二极管各类特征参量对时间常数的作用不一样.低频条件下,二极管的时间常数由材料本身来决定,与外加电流频率无关.高频情况下,时间常数则与半导体材料性质无关,只由外加交流电的频率来决定. 关键词： p-n结二极管 时间常数 载流子 分界面     

p-n结二极管结区边界附近的交流电特性

基于p-n结二极管的理想工作状态的基本假定，推导了二极管在交流电下工作时其基区和p-n结分界面附近上的时间常数与二极管空间尺寸、扩散长度、载流子寿命和外加交流电频率等的依赖关系.结果发现高频和低频两种状态下二极管各类特征参量对时间常数的作用不一样.低频条件下，二极管的时间常数由材料本身来决定，与外加电流频率无关.高频情况下，时间常数则与半导体材料性质无关，只由外加交流电的频率来决定.     

Surface conductivity of cuprous-oxide rectifiers

The physical nature of the surface conductivity of cuprous-oxide rectifiers, the existence of which was indicated by the authors (Fizika tverdogo tela,2, 857, 1960) is investigated. It is shown that this effect is not caused by surface conductivity of the cuprous oxide, but is due to the presence of a conduction channel along the edge of the p-n junction. The effect of humidity and the vapors of various liquids on the surface conductivity of rectifiers is investigated. The results obtained are discussed and a mechanism to explain the presence of a conduction channel at the p-n junction of cuprous-oxide rectifiers is suggested.The authors gratefully acknowledge their indebtedness to S. M. Margolin and M. A. Mishin for making available the rectifiers used in the investigation.     

Analysis of transition processes in semiconductor diodes using charge formula

The transition processes in a narrow-base semiconductor diode are analyzed by a charge method taking account of the p-n junction barrier capacitance. It is shown that the on and off transition switching processes of a diode can be described by three experimentally determined parameters.