Numerical study of surface charge effects on a p-n junction model system: Modulation of junction potential,band diagrams,and recombinations

We theoretically investigate the surface charge effects on a p-n junction model system. It is calculated that the polarity of the surface charges around the junction interface induces different variations in the built-in potential, which has been demonstrated to affect the band diagrams of p-n junction systems. That is, the more negative the surface charge is, the more the built-in potential decreases, and vice versa for positive surface charges in the system. These surface charges affect the modulation of three recombination processes, i.e. the Shockley-Read-Hall, band-to-band, and Auger recombination processes, and are numerically investigated with different surface charge densities imposed at the junction interface. As a result, it is calculated that the three recombination rates are reduced with increasing magnitudes of surface charge density due to the free carrier depletion that occurs around the p-n junction regions.     

Appealing analogies for aiding student's assimilation of some keyphysical concepts related to semiconductor devices

Appealing analogies are proposed to elucidate two important fundamental topics related to semiconductor devices, namely the carrier scattering in a crystal and the derivation of the diffusion capacitance of a p-n junction. The motion of an electron in a semiconductor crystal, according to Schrodinger's wave equation, is likened to that of a photon in a dielectric medium, such as glass, as per Maxwell's electromagnetic wave equations. A circuit analogy is given to clarify and contrast quasistatic and rigorous techniques of deriving the diffusion capacitance of a p-n junction. The analogies capture all aspects of these topics, highlight the important fundamental issues that may escape an average student's notice, and remove any confusion that may exist in the student's mind because of different and partial treatments of the topics in existing textbooks. Exposure to these and other analogies also plays a role in developing analogical reasoning among students who may pursue research     

Fabrication and electrical characterization of solution-processed all-oxide transparent NiO/TiO2 p-n junction diode by sol–gel spin coating method

Solution-processed all-oxide transparent NiO/TiO₂ p-n junction was fabricated using sol–gel spin coating method. The optical properties of the NiO and TiO₂ films were studied by transmittance and absorbance spectra. The optical band gaps of NiO and TiO₂ films were determined by optical absorption method and found to be 3.83 eV and 3.74 eV, respectively. The current–voltage characteristics of the oxides based p-n junction showed a rectifying behavior. The junction parameters such as ideality factor and barrier height were calculated using thermionic emission model, Chenug, and Norde method. The barrier height and ideality factor values of the diode were obtained to be 0.59 eV and 9.8, respectively.     

柔性单晶锗PIN二极管在关态下的建模研究

介绍了柔性单晶锗纳米薄膜（GeNM ）PIN 二极管的制备方法和反向偏置下对应不同弯曲状态下的射频特性。为了定量研究在反向偏置下机械弯曲对柔性PIN二极管射频特性的影响，分别搭建了不同弯曲半径下的等效电路模型。通过研究不同机械应力作用下模型中的各个参数的变化得到二极管内部电阻，寄生电感，p＋ p-结的电阻以及p-n＋结的电容为影响其射频特性的主要因素，机械弯曲使这些参数值单调变化，导致柔性单晶锗PIN二极管关态下的射频特性变好。这在应变测量领域显示出很大的发展应用潜力。     

New capacitance–voltage model for linearly graded junction

In this work, we present a new model to derive charge and capacitance–voltage (C–V) characteristics for linearly graded p–n junction under reverse polarization using pseudo-equilibrium approach. Furthermore, we propose a compact C–V model under any polarization for this junction type.     

Performance Evolutions of Carrier Depletion Silicon Optical Modulators: From p-n to p-i-p-i-n Diodes

The performance evolution of p-n, p-i-n, and p-i-p-i-n optical modulators based on free-carrier concentration variation is studied. Main figures of merit are recalled for such devices and used to compare one structure to another. The modulation efficiency, optical loss, and −3 dB cutoff frequency are thus optimized for each sort of studied junction. General performance results are presented and discussed at the end.      

Simple unified elucidations of some semiconductor device phenomena

Unification is the quest of science. This paper elucidates unified perspectives of the topics, namely, semiclassical carrier transport in the bulk of a semiconductor and the capacitance of a p-n junction, clarifying the unifying features of drift, diffusion and thermoelectric currents in the former, and of the depletion and diffusion capacitances in the latter, to an extent not achieved in available books. The elucidation should be helpful in raising the comfort and retention levels and developing the theory building capacities of an average student studying the subject of semiconductor devices     

Reliability of InGaAs waveguide photodiodes for 40-Gb/s optical receivers

The reliability of 1.55-/spl mu/m wavelength InGaAs waveguide photodiodes (WGPDs) fabricated by metal-organic chemical vapor deposition is investigated for 40-Gb/s optical receiver applications. Reliability for both high-temperature storage and accelerated life tests obtained by monitoring both the dark current and the breakdown voltage is examined. The median device lifetime and the activation energy of the degradation mechanism are extracted for WGPD test structures. The device lifetimes are examined via statistical analysis which is highly reliable in predicting the device lifetime under practical conditions. The degradation mechanism for the WGPD test structures can be explained by the formation of leakage current path by ionic impurities in the passivation layer on the exposed p-n junction. Nevertheless, it can be concluded that the WGPD test structures exhibit sufficient reliability for practical 40-Gb/s optical receiver applications.     

太阳能电池工作原理简介

当太阳光照射p-n结时，在半导体内的电子由于获得了光能而释放电子，相应地便产生了电子——空穴对，并在势垒电场的作用下，电子被驱向n型区，空穴被驱向P型区，从而使凡区有过剩的电子，P区有过剩的空穴。于是，就在p-n结的附近形成了与势垒电场方向相反的光生电场。     

Photoconducting properties of Cd0.4ZnO0.6/p-Si photodiode by sol gel method

Al/Cd_0.4ZnO_0.6/p-Si Schottky photodiode was successfully fabricated via sol–gel process. The current–voltage characteristics of the diode were performed in dark and illumination conditions. The electronic parameters of the diode were determined using the thermionic emission theory. The values of ideality factor (n) and barrier height (Φ_B0) values of the diode were found to be about 5.80 and 0.80 eV, respectively. The photocurrent results in the reverse bias of the diode indicate that the current under illumination is higher than the dark current. The capacitance-voltage (C–V) and conductance-voltage (G–V) measurements of the diode were carried out in the range of 50 kHz–1 MHz. The observed decrease in the capacitance and increase in the conductance with the increasing frequency were explained on the basis of interface states. The obtained results indicate that Cd_0.4ZnO_0.6/p-Si junction is a Schottky type photodiode.     

Space charge capacitance of ferroelectric memory cells in the nonlinear regime

Abstract

Recently ferroelectric thin-film capacitors have been modelled using the sub-surface space charge region. The model is similar to the well known abrupt p-n junction theory or semiconductors. This paper describes the sub-surface space charge using the landau free energy within a polarized medium. The capacitance of the ferroelectric storage cell is described from these first principles. The model predicts that the result of the abrupt p-n junction depletion capacitance (linear medium model) is the limit of the ferroelectric p-n junction model (non-linear medium) when the polarization approaches zero. The results of the model are applied successfully to 60/40 PZT capacitors where the intrinsic heterogeneity (high electron concentration in the near surface region) is always present due to high oxygen vacancy concentration. Both the linear and the nonlinear models are reasonable at high voltages but only the non-linear model is accurate at lower voltages. The results are also useful to characterize device parasitics and elucidate the effect of the microstructure on device behavior.     

晶硅材料太阳电池电势诱导衰减问题研究

传统晶硅材料太阳电池所发生的电势诱导衰减现象受可动电荷Na~+在硅表面聚积的影响,对发生电势诱导衰减现象的太阳电池的漏电区域和非漏电区域分别采用双电荷层导致p-n结导通的假说和扩展的肖克莱-里德-霍尔复合模型进行了研究。结果表明,组件效率受可动电荷Na~+的影响且和被SiN_x的场钝化作用所屏蔽的隐性缺陷之间的关系密切。通过增强界面的钝化效果,阻止Na~+与界面处的隐性缺陷相结合等措施,有利于抗电势诱导衰减组件的制备。     

Micromechanical optoelectronic switch and amplifier (MIMOSA)

We report for the first time the monolithic integration of a micromechanical modulator and a p-n photodiode on a silicon substrate yielding a versatile optoelectronic device. Because both devices are monolithically integrated on a silicon substrate, the combination is compact with minimal parasitic elements. We demonstrate that such a device combination fields a transistor-like element with positive and negative small-signal voltage amplification. The maximum small-signal voltage gain achieved is 500 while the modulated current of the device exhibits a maximum ON-OFF ratio of 3:1. In addition, while the theoretical current gain of the device is infinite, a 10-pA noise level limited the measured dc current gain to 10⁶     

Piezoelectric Effects on the Shockley-Read-Hall Generation Currents in a p-n Junction

We numerically studied the correlation between the piezoelectric effect and the Shockley-Read-Hall (SRH) generation current by examining the defect states within the depletion region (space charge region, w) in a piezoelectric p-n junction system consisting of piezo (n-type: n-ZnO) and non-piezo (p-type: P3HT) parts. Through finite element method calculations, it was demonstrated that the electric potential, owing to the external compressive pressure (T_z) generating negative piezoelectric charges at the p-n interface, becomes more negative. Correspondingly, as T_z increases, so does the number of states depleted of free carriers (depletion region shifts). These observations were confirmed by the increase in the z-component of the electric field distribution and the SRH generation currents, given that current is proportional to the w (T_z).     

GaAsSb: a novel material for near infrared photodetectors on GaAs substrates

We have studied the molecular beam epitaxy (MBE) growth of GaAsSb on GaAs substrates. The optical properties and composition of GaAsSb layer strongly depend on the growth temperature, the Ga growth rate, and the As and Sb fluxes and their ratios. We also report on two GaAsSb-GaAs photodiode structures operating at 1.3 /spl mu/m. The peak quantum efficiency was 54% for the GaAsSb resonant-cavity-enhanced (RCE) p-i-n photodiode and 36% for the RCE GaAsSb avalanche photodiode (APD) with separate absorption, charge, and multiplication regions (SACM). At 90% of the breakdown, the dark current of the SACM APD was 5 nA. The GaAsSb SACM APD also exhibited very low multiplication noise and k/sub eff/ was approximately 0.1, which is the lowest ever reported for APDs operating at 1.3 /spl mu/m.     

Strategies for improving neural signal detection using a neural-electronic interface

There have been various theoretical and experimental studies presented in the literature that focus on interfacing neurons with discrete electronic devices, such as transistors. From both a theoretical and experimental perspective, these studies have emphasized the variability in the characteristics of the detected action potential from the nerve cell. The demonstrated lack of reproducible fidelity of the nerve cell action potential at the device junction would make it impractical to implement these devices in any neural prosthetic application where reliable detection of the action potential was a prerequisite. In this study, the effects of several different physical parameters on the fidelity of the detected action potential at the device junction are investigated and discussed. The impact of variations in the extracellular resistivity, which directly affects the junction seal resistance, is studied along with the impact of variable nerve cell membrane capacitance and variations in the injected charge. These parameters are discussed in the context of their suitability to design manipulation for the purpose of improving the fidelity of the detected neural action potential. In addition to investigating the effects of variations in these parameters, the applicability of the linear equivalent circuit approach to calculating the junction potential is investigated.     

一种混合耦合电感和开关电容的DC-DC升压变换器

为满足工业应用中高电压增益DC-DC变换器的要求,在基本boost变换器基础上,利用耦合电感和开关电容技术,研究了一种具有高电压变比的boost变换器。该变换器将耦合电感和电容混合连接,通过耦合电感对电容进行充电,提高升压变比,而且开关管和二极管等功率器件的电压应力能够得到有效降低,同时耦合电感漏感的能量可以回收和再利用,有利于提高变换器的效率。详细分析了该变换器的工作原理和稳态特性,最后通过搭建一个实验样机,验证了理论分析的正确性。     

Insulator surface charge accumulation under impulse voltage

The surface charge distribution under impulse voltage is measured using a static capacitance probe. A probe with very small charge leakage is designed. The condition of surface charge accumulation under impulse voltage is analyzed, and it is concluded that micro discharges in the gas near the insulator surface such as the corona caused by free and fixed metal particles is usually a prerequisite condition. The dynamic equation describing the relationship between surface charge density and the applied voltage is established, and the process of surface charge accumulation under impulse voltage is analyzed. Theoretical analysis and experimental results show that the decrease of wave front time of the impulse voltage can result in an increase of surface charge accumulation. A GIS spacer is used to investigate the influence of charge accumulation on the flashover characteristics. It is shown that the 50% impulse flashover voltage can be reduced by 23.4%, and the lower limit of the V-t characteristics can be lowered drastically if the polarity of the surface charge is opposite to that of the applied voltage.     

Tunable Dual Band Filter with BST Capacitors

A tunable double band band-stop filter based on BST is presented. This configuration has a coplanar microstrip loaded with stepped impedance resonators. Ferroelectric BST parallel plate capacitors were loaded at the end of the stepped impedance resonators. When a DC voltage is applied to the BST capacitors, the change in capacitance shifts the resonance frequency of the stepped impedance transformers. The filters were designed with notch frequencies at 1.5 GHz and 3.5 GHz without loading them with BST capacitors. The filter circuits were simulated with Agilent ADS and were fabricated on FR-4 substrates. By loading the resonators with BST capacitors with no DC applied voltage, the first and second notch frequency shifts significantly. The first notch frequency can be tuned from 570 MHz to 781 MHz and the second notch frequency from 2.16 GHz to 2.55 GHz by applying the bias voltage of 5volts. The performance of the BST tuned filters were compared with filters tuned with p-n junction varactors.     

零电压开关多谐振三电平直流变换器

该文提出一族零电压开关多谐振三电平直流变换器(Zero-voltage-switching multi-resonant three-leve lconverters，ZVS-MR-TLCs)，它是在三电平变换器的基础上加入LCC谐振网络实现ZVS，开关管和二极管的结电容以及变压器的漏感被利用。该文以Buck ZVS-MR-TLC为例分析它的工作原理和特性，并与传统的两电平零电压开关多谐振变换器(ZVS-MRC)进行比较。与两电平ZVS-MRC相比，ZVS-MR-TLC功率器件的电压应力降低，实现ZVS的负载范围变宽，滤波电感和滤波电容大大减小。最后给出了实验结果。