Similar admittance behavior of amorphous silicon carbide and nitride dielectrics within the MIS structure

PECVD grown a-SiNx:H and a-SiCx:H films were investigated as dielectric films in the form of metal/insulator/p-silicon (MIS) structures. AC admittance of MIS structures was measured as a function of dc gate bias voltages and frequencies (1-1000 kHz) of the superimposed ac bias voltage (10 mV). For each applied bias voltage (from accumulating to inverting bias regimes), temperature (T) dependence of both capacitance (C) and conductance (G/ω) were measured to investigate majority/minority carrier behavior under various frequencies ω (kHz-MHz) as parameters. C and G/ω-T-ω measurements reveal that observed pairs of capacitance steps and conductance peaks are related to traps lying on the same energy value, residing in the insulator and at the interface of insulator/semiconductor structure and differing only through capture cross-sections. On the other hand, surface band bending (ψ_s) of silicon and activation energy (E_A) deduced from the Arrhenius plot of the frequency vs. reciprocal temperature as a function of gate bias (V_G) seem linearly dependent, implying that E_A reflects the ψ_s variation.     

WCL调节仪在串级控制中的应用

在介绍WCL-13A调节仪特点和基本规格的基础上,着重介绍了串级控制技术和WCL-13A这种新型调节仪在太阳能电池制造中的扩散炉温度控制等场合的应用案例。     

千赫及兆赫级频带EMI技术检测灵敏度实验研究

借助WK6500B精密阻抗分析仪对压电阻抗(EMI)技术结构健康监测研究中,检测频带与检测灵敏度间的关系进行了定量研究.选用尺寸为1 250 mm×100 mm×3 mm铝梁结构上距离锆钛酸铅压电陶瓷(PZT)传感器1 000 mm的(φ)1.2 mm通孔损伤作为检测对象.在10 kHz～10MHz频率范围内7个峰值集中的频段,分别选用电阻抗谱峰值偏移量(△f)和均方差作为损伤识别指数,对EMI技术检测灵敏度进行了研究.结果表明,在千赫级频带范围内,△f和均方差均随着检测频段的升高呈先增大后减小的变化趋势,280～340 kHz频段对于通孔损伤具有最高的检测灵敏度.在兆赫级频带范围内,△f取值较大,在6.18 MHz处出现了25.0 kHz的显著偏移.由于千赫和兆赫级频带的电阻抗信号分别具有峰值数量多,综合各峰值信息整体分析时对损伤敏感和峰值数量少,单一峰值偏移量对损伤敏感的特点,在实际检测过程中,可将这2个频带的检测结果结合起来以提高EMI技术对微小损伤的检测灵敏度.     

New explicit current/voltage equation for p‐i‐n solar cells including interface potential drops and drift/diffusion transport

Analytical modeling of p‐i‐n solar cells constitutes a practical tool to extract material and device parameters from fits to experimental data, and to establish optimization criteria. This paper proposes a model for p‐i‐n solar cells based on a new approximation, which estimates the electric field taking into account interface potential drops at the intrinsic‐to‐doped interfaces. This leads to a closed‐form current/voltage equation that shows very good agreement with device simulations, revealing that the inclusion of the interface potential drops constitutes a major correction to the classical uniform‐field approach. Furthermore, the model is able to fit experimental current/voltage curves of efficient nanocrystalline Si and microcrystalline Si p‐i‐n solar cells under illumination and in the dark, obtaining material parameters such as mobility‐lifetime product, built‐in voltage, or surface recombination velocity. Copyright © 2012 John Wiley & Sons, Ltd.     

Solution processed high band‐gap CuInGaS2 thin film for solar cell applications

A high band‐gap (~1.55 eV) chalcopyrite compound film (CuInGaS₂) was synthesized by a precursor solution‐based coating method with an oxidation and a sulfurization heat treatment process. The film revealed two distinct morphologies: a densely packed bulk layer and a rough surface layer. We found that the rough surface is attributed to the formation of Ga deficient CuInGaS₂ crystallites. Because of the high band‐gap optical property of the CuInGaS₂ absorber film, a solar cell device with this film showed a relatively high open circuit voltage (~787 mV) with a power conversion efficiency of 8.28% under standard irradiation conditions. Copyright © 2013 John Wiley & Sons, Ltd.     

高性能CIC抽取滤波器研究与设计

针对采样率变换系统中CIC抽取滤波器存在通带失真较大和阻带衰减较小的问题,提出一种高性能CIC抽取滤波器的设计方法,该方法采用补偿滤波器技术和非递归并行结构.仿真结果表明,通带失真与阻带衰减特性明显优于传统的CIC,CIC-Cosine,ISOP-CIC等滤波器.因此,适用于对幅频特性要求较高的采样率变换系统.     

超宽带微波光发射机关键技术

介绍了超宽带微波信号光发射机的工作原理,对使用中存在的外调制器偏置控制点漂移、超宽带微波光发射机非线性失真等问题进行了系统分析,给出了自动偏置控制及预失真补偿等解决方案,通过采用这些关键技术成功设计完成了超宽带微波光发射机.     

Intermediate band photovoltaics based on interband–intraband transitions using In0.53Ga0.47As/InP superlattice

We present a theoretical model to incorporate the quantum mechanism of two‐photon transitions into macroscopic operations. The two‐photon transition is described as a two‐step interband–intraband transition within the one‐band envelope‐function framework and is coupled with drift–diffusion as well as the potential distribution. In_0.53Ga_0.47As/InP superlattices (SLs) are chosen as the initial candidate to simulate intermediate band solar cell operation. In this type of structure, the absorption spectrum of interband and intraband transitions is asymmetric and strongly depends on device structure and operating conditions. Our results also reveal that the intraband transition dominates the detailed balance. Both the intermediate band (IB) configuration and the conversion efficiency are determined by the SL structure. Only well‐designed SLs can form the appropriate IB. Furthermore, an efficiency contour plot has been calculated to guide quantum design: the peak efficiency is 45.61% when the well thickness is 4 nm and the barrier thickness is 2 nm. As the well or barrier thickness increases to 10 nm, the absorption peak of the intraband transition gradually redshifts and narrows, so the efficiency correspondingly decreases to below 40%. Copyright © 2011 John Wiley & Sons, Ltd.     

Absorption coefficient for the intraband transitions in quantum dot materials

In this paper, we present calculations of the absorption coefficient for transitions between the bound states of quantum dots grown within a semiconductor and the extended states of the conduction band. For completeness, transitions among bound states are also presented. In the separation of variables, single band k·p model is used in which most elements may be expressed analytically. The analytical formulae are collected in the appendix of this paper. It is concluded that the transitions are strong enough to provide a quick path to the conduction band for electrons pumped from the valence to the intermediate band. Copyright © 2012 John Wiley & Sons, Ltd.     

Design of dual-band bandpass coplanar waveguide filter

Several recent applications in communications require filters that can operate in two or more frequency bands. The aim of this article is to exploit the advantages of coplanar waveguides (CPWs) to design a dual-band bandpass coplanar waveguide filter (DBBPF). Starting from the prototype of a two pole Chebyshev low pass filter, two frequency transformations are applied to generate the DBBPF's lumped equivalent circuit. These circuits are then implemented using compact CPW series-connected resonators patterned in the centre conductor. The designed filter operates at the two frequency bands centred at 1.7 GHz and 2.7 GHz. Measured results are obtained and compared to HFSS-simulated results with very good agreement.