Barrier height and ideality factor dependency on identically produced small Au/p-Si Schottky barrier diodes

Small high-quality Au/P-Si Schottky barrier diodes（SBDs） with an extremely low reverse leakage current using wet lithography were produced.Their effective barrier heights（BHs） and ideality factors from current-voltage （Ⅰ-Ⅴ） characteristics were measured by a conducting probe atomic force microscope（C-AFM）.In spite of the identical preparation of the diodes there was a diode-to-diode variation in ideality factor and barrier height parameters.By extrapolating the plots the built in potential of the Au /p-Si contact was obtained as V_（bi）=0.5425 V and the barrier height valueΦ_（b（c-V）） was calculated to beΦ_（B（C-V））=0.7145 V for Au/p-Si.It is found that for the diodes with diameters smaller than 100μm,the diode barrier height and ideality factor dependency to their diameters and correlation between the diode barrier height and its ideality factor are nonlinear,where similar to the earlier reported different metal semiconductor diodes in the literature,these parameters for the here manufactured diodes with diameters more than 100μm are also linear.Based on the very obvious sub-nanometer C-AFM produced pictures the scientific evidence behind this controversy is also explained.

Determination of the Electrical Parameters of a Solar Cell in Steady State

Photovoltaic solar energy can be obtained by using several types of technologies, including silicon solar cells. The characterization of its solar cells makes it possible to know them better. This article presents, on the one hand, the work that has been carried out on these cells. On the other hand, a theoretical study of the cell under illumination using Lambert’s W function. On the basis of the electrical parameters provided by the manufacturer, the parameters such as the series and shunt resistances and the electrical quantities such as the photocurrent and the photovoltage, are determined and studied according to the ideality factor of the diode. From the results obtained the shunt resistance increases when the ideality factor increases, the series resistance decreases very weakly.

Analysis on electrical characteristics of high-voltage GaN-based light-emitting diodes

In order to investigate their electrical characteristics, high-voltage light-emitting-diodes （HV-LEDs） each contain- ing four cells in series are fabricated. The electrical parameters including varying voltage and parasitic effect are studied. It is shown that the ideality factors （IFs） of the HV-LEDs with different numbers of cells are 1.6, 3.4, 4.7, and 6.4. IF increases linearly with the number of cells increasing. Moreover, the performance of the HV-LED with failure cells is examined, The analysis indicates that the failure cell has a parallel resistance which induces the leakage of the failure cell. The series resistance of the failure cell is 76.8 Ω, while that of the normal cell is 21.3 Ω. The scanning electron microscope （SEM） image indicates that different metal layers do not contact well. It is hard to deposit the metal layers in the deep isolation trenches. The fabrication process of HV-LEDs needs to be optimized.

Thermal annealing behaviour of Al/Ni/Au multilayer on n-GaN Schottky contacts

Recently GaN-based high electron mobility transistors （HEMTs） have revealed the superior properties of a high breakdown field and high electron saturation velocity. Reduction of the gate leakage current is one of the key issues to be solved for their further improvement. This paper reports that an Al layer as thin as 3 nm was inserted between the conventional Ni/Au Schottky contact and n-GaN epilayers, and the Schottky behaviour of Al/Ni/Au contact was investigated under various annealing conditions by current-voltage （I-V） measurements. A non-linear fitting method was used to extract the contact parameters from the I-V characteristic curves. Experimental results indicate that reduction of the gate leakage current by as much as four orders of magnitude was successfully recorded by thermal annealing. And high quality Schottky contact with a barrier height of 0.875 eV and the lowest reverse-bias leakage current, respectively, can be obtained under 12 min annealing at 450 ℃ in N2 ambience.

On the reverse leakage current of Schottky contacts on free-standing GaN at high reverse biases

In this work, a dislocation-related tunneling leakage current model is developed to explain the temperature-dependent reverse current–voltage（I–V –T） characteristics of a Schottky barrier diode fabricated on free-standing GaN substrate for reverse-bias voltages up to-150 V. The model suggests that the reverse leakage current is dominated by the direct tunneling of electrons from Schottky contact metal into a continuum of states associated with conductive dislocations in GaN epilayer.A reverse leakage current ideality factor, which originates from the scattering effect at metal/GaN interface, is introduced into the model. Good agreement between the experimental data and the simulated I–V curves is obtained.

High-temperature current conduction through three kinds of Schottky diodes

Fundamentals of the Schottky contacts and the high-temperature current conduction through three kinds of Schottky diodes are studied. N-Si Schottky diodes, GaN Schottky diodes and AlGaN/GaN Schottky diodes are investigated by I-V-T measurements ranging from 300 to 523 K. For these Schottky diodes, a rise in temperature is accompanied with an increase in barrier height and a reduction in ideality factor. Mechanisms are suggested, including thermionic emission, field emission, trap-assisted tunnelling and so on. The most remarkable finding in the present paper is that these three kinds of Schottky diodes are revealed to have different behaviours of high-temperature reverse currents. For the n-Si Schottky diode, a rise in temperature is accompanied by an increase in reverse current. The reverse current of the GaN Schottky diode decreases first and then increases with rising temperature. The AlGaN/GaN Schottky diode has a trend opposite to that of the GaN Schottky diode, and the dominant mechanisms are the effects of the piezoelectric polarization field and variation of two-dimensional electron gas charge density.

Comparative study of the electrical properties of Au/n-Si(MS) and Au/Si_3N_4 /n-Si(MIS) Schottky diodes

In this paper, the electrical parameters of Au/n-Si （MS） and Au/Si3N4/n-Si （MIS） Schottky diodes are obtained from the forward bias current-voltage （I-V） and capacitance-voltage （C-V） measurements at room temperature. Experimental results show that the rectifying ratios of the MS and MIS diodes at ± 5 V are found to be 1.25 ×103 and 1.27 ×104, respectively. The main electrical parameters of the MS and MIS diodes, such as the zero-bias barrier height （rbBo） and ideality factor （n）, are calculated to be 0.51 eV （I-V）, 0.53 eV （C-V）, and 4.43, and 0.65 eV （I-V）, 0.70 eV （C-V）, and 3.44, respectively. In addition, the energy density distribution profile of the interface states （Nss） is obtained from the forward bias I-V, and the series resistance （Rs） values for the two diodes are calculated from Cheung＇s method and Ohm＇s law.

A Simplified Simulation Procedure and Analysis of a Photovoltaic Solar System Using a Single Diode Model

A single diode model for a photovoltaic solar module is the most ideal and quick way of analyzing the module characteristics before implementing them in a solar plant. Solar modules manufacturers provide information for three critical points that are essential in I-V, P-V or P-I curves. In this study, we propose four separate simulation procedures to estimate the five-model parameters of an analogous single diode equivalent circuit by utilizing three cardinal points of the photovoltaic module I-V curve, described from experimental data using a solar simulator and manufacturer’s datasheet. The main objective is to extract and use the five unknown parameters of a single diode model to describe the photovoltaic system using I-V ad P-V plots under different environmental conditions. The most influential parameters that greatly alter the cardinal points defined at short circuit point (SCP), the maximum power point (MPP) and the open circuit point(OCP) are the ideality factor (n) and the diode saturation current (Io). For a quick and fast convergence, we have determined the optimal ideality factor (no) and optimal saturation current (Ioopt) as the primary parameters by first assuming the optimal values of Rsh, Rs and Iph at standard test conditions (STC). Further, we evaluated the effects of Iph, Rs and Rsh on I-V and P-V curves by considering the values of n below no. We have evaluated different iterative procedures of determining Rsh and Rs at open-circuit, short-circuit point and the maximum-power points. These procedures have been classified into four approaches that guarantees positive shunt and series resistance for n ≤ no. These approaches have been categorized by deriving the saturation current as a dependent variable at each cardinal point with or without Rs and Rsh pair. The values obtained for the five parameters have been used to simulate the photovoltaic solar module characteristic curves with great precision at different air temperatures and irradiances, considering the effect of Nominal Operating Cell Temperature (NOCT).

Facile lattice tensile strain compensation in mixed-cation halide perovskite solar cells

Despite the rapid development of power conversion efficiency(PCE)for halide perovskite solar cells(PSCs),the lattice strain engineering in perovskite thin films has been rarely probed in recent years.Herein,a strain compensation by homogeneous crystallization in perovskite films is achieved with the aid of precursor aging in the mixed-cation perovskite of Cs_(0.05)(FA_(0.83)MA_(0.17))Pb(I_(0.90)Br_(0.10))_(3)with near 20%PCE in inverted devices.The homogeneous crystallization releases the residual tensile stress and induces more compressive stress at the edges of perovskite films,thus elongating the carrier lifetime and reducing the trap-assisted carrier recombination.The high dependence on the perovskite components in strain engineering strategy was systematically revealed,wherein MAPbI_(3)and Cs_(0.05)(FA_(0.83)MA_(0.17))PbI_(3)film showed an increased compressive strain and FAPbI3 film showed adverse tensile strain after aging.The density functional theory(DFT)calculations are further performed to reveal the change of electronic features.The precursor aging-induced strain modulation was correlated with a systematic characterization of the charge carrier transport and recombination dynamics in the mixed-cation perovskite films.We believe that this facile approach provides a novel strain engineering strategy for PSCs technology.

Investigation into charge carrier dynamics in organic light-emitting diodes

Organic light-emitting diodes(OLEDs)have demonstrated remarkable advancements in both device lifetime and luminous efficiency.However,insufficient operation lifetime due to device degradation remains a major hurdle,especially for brighter devices.Understanding the degradation mechanisms of OLEDs due to the degradation of functional materials and the formation of defects in device architectures continues to be a significant challenge.Herein,we evaluate the degradation characteristics by scrutinizing the electrical and optical properties,as well as analyzing the charge carrier dynamics in pristine and aged states of phosphorescent OLEDs(PhOLEDs).We show that degradation mechanisms in PhOLEDs can be elucidated in terms of the ideality factors of current and luminance in pristine and aged device states.The consistent shifts in distinct ideality factors across various states points out that the device degradation is attributed to the deterioration of the guest material,i.e.green-light-emitting phosphorescent material.Conversely,the incongruity in ideality factor changes between the two states indicates that the degradation results from the deterioration of non-light-emitting material.Subsequent characterization experiments provide further evidence that this degradation is primarily attributed to the deterioration of CBP-host material.The thorough understanding of degradation mechanisms established in this study can contribute to realizing the highly reliable PhOLEDs with a long lifetime.

Diode parameter extraction by a linear cofactor difference operation method

The linear cofactor difference operator（LCDO） method,a direct parameter extraction method for general diodes,is presented.With the developed LCDO method,the extreme spectral characteristic of the diode voltage-current curves is revealed,and its extreme positions are related to the diode characteristic parameters directly.The method is applied to diodes with different sizes and temperatures,and the related characteristic parameters,such as reverse saturation current,series resistance and non-ideality factor,are extracted directly.The extraction result shows good agreement with the experimental data.

Effect of temperature on the intensity and carrier lifetime of an AlGaAs based red light emitting diode

The influence of temperature on the intensity of light emitted by as well as the carrier life time r of a standard A1GaAs based light emitting diode has been investigated in the temperature range from 345 to 136 K. The open-circuit voltage decay （OCVD） technique has been used for measured the carrier lifetime. Our experimental results reveal a 16% average increase in intensity and a 163.482-19.765 ns variation in carrier lifetime in the above temperature range. Further, theoretical and experimental analysis show that for negligible carrier density the intensity is inversely proportional to carrier lifetime for this sample.

Influence of temperature on tunneling-enhanced recombination in Si based p–i–n photodiodes

We investigate the dominant dark current transport mechanism in Si based p-i-n photodiodes, namely, BPW 21R, SFH 205FA and BPX 61 photodiodes in the temperature range of 350 to 139 K. The forward current- voltage characteristics of these photodiodes are explained via the tunneling enhanced recombination model, which gives a quantitative description of the electronic mechanism in the p-i-n junction photodiodes. The observed tem- perature dependence of the saturation current and the diode ideality factor of these devices agree well with theo- retical predictions; the analysis also indicates the importance of doping for enhancement of tunneling. The present study will be helpful in applying the devices at low temperature ambience.

Effect of single walled carbon nanotubes on series resistance of Rose Bengal and Methyl Red dye-based organic photovoltaic device

The influence of single walled carbon nanotube（SWCNT）on the series resistanceof Rose Bengal（RB）and Methyl Red（MR）dye-based organic diodes has been studied.It has been revealed from experimental results that SWCNT has a significant effect on Rs.The values of Rs are measured from current–voltage（I–V）characteristics and also by utilizing the Cheung method.Obtained values from the Cheung method have been verified using H（I）–I plots for all dye-based devices.The extracted values using these two processes show a good consistency with each other.It is observed that Rs is reduced significantly by incorporating SWCNT for both dyes.The estimated amounts of reduction of Rs using SWCNT are 76.08%and 64.23%obtained from the I–V relationship whereas the value of Rs shows a reduction of 83.5%and 67.1%when measured by using the Cheung method for RB and MR dyes respectively.The ideality factor and barrier height of the diodes have also been extracted.The ideality factor has decreased with incorporation of SWCNT.A reduction in barrier height for the devices has also been observed in the presence of SWCNT.

Analysis of the electrical characteristics of GaInP/GaAs HBTs including the recombination effect

An analytical model is used to predict the effects of surface recombination current on the gain and transit time of GalnP/GaAs heterojunction bipolar transistors（HBTs）.The present analysis shows that consideration of the recombination current gives current gain values that are comparable to those of the experimental results.The dependence of current gain on temperature,base doping and emitter area are also analyzed,and the variation in collector current with emitter-base voltage,temperature and doping is considered.

Accurate surface potential determination in Schottky diodes by the use of a correlated current and capacitance voltage measurements.Application to n-InP

Based on current voltage（I-Vg） and capacitance voltage（C-Vg） measurements,a reliable procedure is proposed to determine the effective surface potential Vd（Vg） in Schottky diodes.In the framework of thermionic emission,our analysis includes both the effect of the series resistance and the ideality factor,even voltage dependent. This technique is applied to n-type indium phosphide（n-InP） Schottky diodes with and without an interfacial layer and allows us to provide an interpretation of the observed peak on the C-Vg measurements.The study clearly shows that the depletion width and the flat band barrier height deduced from C-Vg,which are important parameters directly related to the surface potential in the semiconductor,should be estimated within our approach to obtain more reliable information.

Fabrication,electrical and photovoltaic characteristics of CuInGeSe4/n-Si diode

The CuInGeSe_4 thin film was deposited onto n-type single crystal silicon wafers by the electron beam deposition technique. The Au/CuInGeSe_4/n-Si/Al heterojunction device has been fabricated. The structure of the CuInGeSe_4 thin film was characterized by X-ray diffraction(XRD), scanning electron microscope(SEM), and energy dispersive X-ray analysis(EDX). The dark current-voltage characteristics of the Au/CuInGeSe_4/n-Si/Al heterojunction diode have been studied at a temperature range of 303-383 K. Also, the photovoltaic properties were examined at different illumination intensities. The capacitance-voltage characteristics of the CuInGeSe_4/n-Si heterojunction were studied at different temperatures in the dark.

Investigation of Illumination Effects on the Electrical Properties of Au/GO/p-lnP Heterojunction with a Graphene Oxide Interlayer

In this work,the electrical property of Au/graphene oxide/p-InP hetero-structure has been evaluated by 1-V and C-V measure-ments in dark and iluminated conditions(visible light).The diode exhibited significant rectifying behavior,thus indicating the heterojunction-lype diode.The key electrical parameters of heterojunction diode including ideality factor(n),series resistance(R),shunt resistance(Rsh),and barrier height(Фb)are estimated from I-V data based on the theory of thermionic emission.The modifed Norde and Cheung's methods were utilized to evaluate the electrical parameters and compared the results.The current conduction mechanism at different voltage regions of I-V has also been investigated.The variation of 1/C versus voltage signifies linearity at high frequency(1 MHz),indicating that the type of heterojunction can be abrupt.The experimental outcomes of this study revealed that the performance of heterojunction diode in dark is considerably good as compared to the ilumination condition with respect to the lower values of Фp,n,R,and interface state density(Nss).