Silicon Schottky Barrier Research Articles

Reliability of Quasi-vertical GaN on Silicon Schottky Barrier Diodes With SiO₂ Passivation Layer Under On-State Stress Bias

Reliability of Quasi-vertical GaN on Silicon Schottky Barrier Diodes With SiO₂ Passivation Layer Under On-State Stress Bias

Investigating the effect of aluminum oxide fixed charge on Schottky barrier height in molybdenum oxide-based selective contacts

A tunneling atomic layer deposited (ALD) AlOx layer was inserted in a Si|SiOx|AlOx|MoOx|metal tunnel diode structure to investigate the impact of fixed interface charge on Schottky barrier height. ALD AlOx provides a synthesis-tunable fixed charge and can provide excellent field effect passivation at the SiOx|AlOx interface. A large (>1 × 1012 q.cm−2) negative fixed charge density was expected to decrease Schottky barrier height on p-type silicon and increase Schottky barrier height on n-type silicon by up to 0.4 eV based on an electrostatic model. Fixed charge density and interface trap state density were measured using a thick layer of AlOx in metal oxide semiconductor capacitor structures (MOSCAPs); Schottky barrier height and specific contact resistivity were measured using a tunneling-active layer of AlOx in contacted structures with MoOx. In some samples, HfOx interface layers were inserted between AlOx and silicon to quench the fixed negative charge. The Schottky barrier height was found to vary with processing conditions but did not have a strong correlation with expected fixed charge density. Thus, while fixed charge may play a role in determining the Schottky barrier height, other parameters also have significant affect. Further work is needed to minimize contact resistivity and elucidate other factors impacting the Schottky barrier height.

The Physics behind the Modulation of Thermionic Current in Photodetectors Based on Graphene Embedded between Amorphous and Crystalline Silicon.

In this work, we investigate a vertically illuminated near-infrared photodetector based on a graphene layer physically embedded between a crystalline and a hydrogenated silicon layer. Under near-infrared illumination, our devices show an unforeseen increase in the thermionic current. This effect has been ascribed to the lowering of the graphene/crystalline silicon Schottky barrier as the result of an upward shift in the graphene Fermi level induced by the charge carriers released from traps localized at the graphene/amorphous silicon interface under illumination. A complex model reproducing the experimental observations has been presented and discussed. Responsivity of our devices exhibits a maximum value of 27 mA/W at 1543 nm under an optical power of 8.7 μW, which could be further improved at lower optical power. Our findings offer new insights, highlighting at the same time a new detection mechanism which could be exploited for developing near-infrared silicon photodetectors suitable for power monitoring applications.

Development of directly grown‐graphene–silicon Schottky barrier solar cell using co‐doping technique

Low-cost, highly efficient, and low-power devices are essential for energy harvesting applications. Despite numerous studies having been conducted on transferable graphene solar cells, large-area growth and long-term stability continue to remain elusive, which limits the practicability of graphene-based photovoltaic devices. Plasma-enhanced chemical vapor deposition is a promising, efficient, and facile method for synthesizing graphene over a large area without the use of a metal catalyst, but defects formed during graphene growth adversely affect the power conversion efficiency (PCE) of graphene/Si solar cells in which the graphene is used. In this work, we successfully employed acid-based graphene-Si macromolecular photovoltaic devices chemically doped with polymeric perfluorinated sulfonic acid (PFSA) macromolecules and nitric acid (HNO3). We achieved an improved PCE of about 9.27% with PFSA doping compared with the value (7.64%) without PFSA doping, and it increased substantially to 10.44% after co-doping with HNO3. PFSA macromolecular doping also led to a substantial increase in the carrier concentration, which helped to reduce the sheet resistance of graphene and improved the work function of the device. In particular, the synergistic effect of co-doping with HNO3 helped to improve the number of active sites and charge separation. Along with the increase in carrier concentration, doping with PFSA reduced the number of defects, resulting in the graphene having a smooth and uniform surface, which effectively increased the open-circuit voltage (Voc) from 0.500 to 0.521 V. We surmise that nonvolatile PFSA macromolecular and volatile HNO3 co-doping has high potential for use in the fabrication of low-cost directly grown-graphene-based photovoltaic devices. Highlights Plasma-enhanced chemical vapor deposition technique used for the direct growth of graphene without metal catalyst. Naturally grown oxide thickness optimized. Nonvolatile macromolecular dopant per-fluorinated polymeric sulfonic acid (PFSA) and volatile nitric acid (HNO3) were used for direct growth graphene doping. The power conversion efficiency of ~9.27% with PFSA doping from 7.64%; further, its substantial increase up to 10.44% after co-doping with HNO3 were achieved with long-term stability.

High performance graphene-silicon Schottky junction solar cells with HfO2 interfacial layer grown by atomic layer deposition

Among the limiting factors that affect the performance of Graphene (Gr)/ Silicon (Si) Schottky barrier solar cells (SBSC) - are the high recombination at Gr/Si interface and the growth of undesirable native oxide that resulted in instability issue. In this work, hafnium oxide (HfO2) grown by atomic layer deposition (ALD) has been investigated as an interfacial layer for Gr/Si Schottky junction solar cells. Engineering the interface with HfO2 contributed to enhancing the power conversion efficiency remarkably from 3.9% to 9.1%. The obtained efficiency with HfO2 interfacial layers grown by ALD is considered among the highest reported for Gr/Si SBSC using pristine graphene.

Interface engineering of graphene-silicon Schottky junction solar cells with an Al2O3 interfacial layer grown by atomic layer deposition.

The recent progress in graphene (Gr)/silicon (Si) Schottky barrier solar cells (SBSC) has shown the potential to produce low cost and high efficiency solar cells. Among the different approaches to improve the performance of Gr/Si SBSC is engineering the interface with an interfacial layer to reduce the high recombination at the graphene (Gr)/silicon (Si) interface and facilitate the transport of photo-generated carriers. Herein, we demonstrate improved performance of Gr/Si SBSC by engineering the interface with an aluminum oxide (Al2O3) layer grown by atomic layer deposition (ALD). With the introduction of an Al2O3 interfacial layer, the Schottky barrier height is increased from 0.843 V to 0.912 V which contributed to an increase in the open circuit voltage from 0.45 V to 0.48 V. The power conversion efficiency improved from 7.2% to 8.7% with the Al2O3 interfacial layer. The stability of the Gr/Al2O3/Si devices was further investigated and the results have shown a stable performance after four weeks of operation. The findings of this work underpin the potential of using an Al2O3 interfacial layer to enhance the performance and stability of Gr/Si SBSC.

Temperature dependent current-voltage characteristics of Au/n-Si Schottky barrier diodes and the effect of transition metal oxides as an interface layer

Temperature dependent current–voltage (I‒V) characteristics of Au/n-type silicon (n-Si) Schottky barrier diodes have been investigated. Three transition metal oxides (TMO) are used as an interface layer between gold and silicon. The basic Schottky diode parameters such as ideality factor (n), barrier height (ϕb0) and series resistance (Rs) are calculated and successfully explained by the thermionic emission (TE) theory. It has been found that ideality factor decreased and barrier height increased with increased of temperature. The conventional Richardson plot of ln(I0/T2) vs. 1000/T is determined the activation energy (Ea) and Richardson constant (A*). Whereas value of ‘A*’ is much smaller than the known theoretical value of n-type Si. The temperature dependent I–V characteristics obtained the mean value of barrier height (ϕb0¯) and standard deviation (σs) from the linear plot of ϕap vs. 1000/T. From the modified Richardson plot of ln(I0/T2) ˗ (qσ)2/2(kT)2 vs. 1000/T gives Richardson constant and homogeneous barrier height of Schottky diodes. Main observation in this present work is the barrier height and ideality factor shows a considerable change but the series resistance value exhibits negligible change due to TMO as an interface layer.

Effect of ultrasound on reverse leakage current of silicon Schottky barrier structure

The influence of ultrasonic loading on reverse current–voltage characteristics of Mo/n–n+–Si structures has been investigated. The research of leakage current variation has been carried out for various ultrasonic wave frequencies (4.1 and 8.4 MHz), intensities (up to 0.8 W/cm2) and loading temperatures (130–330 K). The observed reversible acoustically induced increase in reverse currents was as large as 60%. It has been found that dominant charge transfer mechanisms are the thermionic emission (at high temperature) and the phonon-assisted tunneling (at low temperature). The ultrasound loading affects both processes due to the decrease of Schottky barrier height and binding energy of the electron on the trap.

Dependence of the Photocurrent of a Schottky-Barrier Solar Cell on the Back Surface Recombination Velocity and Suggestion for a Structure with Improved Performance

Though Schottky-barrier solar cells have been studied extensively previously, not much work has been done recently on these cells, because of the fact that conventional p-n junction silicon solar cells have much higher efficiency and have attracted the attention of most of the researchers. However, the Schottky-barrier solar cells have the advantage of simple and economical fabrication process. In this paper, the effect of back surface recombination velocity on the minority carrier distribution and the spectral response of a Schottky-barrier silicon solar cell have been investigated and, based on this study, a new design of the cell with a back surface field has been suggested, which is expected to give much improved performance.

Computational Study on the Electrical Behavior of Silicon Nanowire Memristive Biosensors

In this paper, a complete study is carried out investigating the relationship between the biosensing and the electrical characteristics of freestanding two-terminal Schottky-barrier silicon nanowires. This paper successfully reproduces computationally the electrical behavior obtained experimentally from the nanowire devices before and after the surface biomodification. Throughout modeling and simulations, this paper confirms that the experimental results obtained from the electrical characterization of bare two-terminal Schottky-barrier silicon nanowires present current-to-voltage characteristics fully equivalent to that of a pure memristor device, according to the literature. Furthermore, this paper shows that the voltage gap appearing in the current-to-voltage characteristics for nanowires with biomodified surface is related to capacitive effects due to minority carriers in the nanowire and it is also indicated that those effects are strongly affected by the concentration of antigens uptaken on the device surface. Overall, this paper confirms the implication of the memristive effect for biosensing applications and therefore, demonstrates the memristive biosensors.

An analytical model for optimizing the performance of graphene based silicon Schottky barrier solar cells

In this paper, a model taking into account the effects of carrier loss mechanisms has been developed. The model simulates the photovoltaic properties of the graphene/n-type silicon Schottky barrier solar cells (G/n-Si_SBSC), and it can reproduce the experimentally determined parameters of the G/n-Si_SBSC. To overcome the low efficiencies of G/n-Si_SBSC, their performances have been optimized by modifying the work function of graphene and Si properties, accounted for variation of its thickness and doping level. The obtained results show that the work function of graphene has the major impact on the device performance. Also, the temperature dependence of the G/n-Si_SBSC performance is investigated.

Role of interfacial oxide in high-efficiency graphene-silicon Schottky barrier solar cells.

The advent of chemical vapor deposition (CVD) grown graphene has allowed researchers to investigate large area graphene/n-silicon Schottky barrier solar cells. Using chemically doped graphene, efficiencies of nearly 10% can be achieved for devices without antireflective coatings. However, many devices reported in past literature often exhibit a distinctive s-shaped kink in the measured I/V curves under illumination resulting in poor fill factor. This behavior is especially prevalent for devices with pristine (not chemically doped) graphene but can be seen in some cases for doped graphene as well. In this work, we show that the native oxide on the silicon presents a transport barrier for photogenerated holes and causes recombination current, which is responsible for causing the kink. We experimentally verify our hypothesis and propose a simple semiconductor physics model that qualitatively captures the effect. Furthermore, we offer an additional optimization to graphene/n-silicon devices: by choosing the optimal oxide thickness, we can increase the efficiency of our devices to 12.4% after chemical doping and to a new record of 15.6% after applying an antireflective coating.

Simple and Accurate Circuit Simulation Model for SiC Power MOSFETs

Simple and accurate circuit simulation models for high-voltage silicon carbide power MOSFETs and Schottky barrier diodes are presented and validated. The models are physics-based and consist of minimal number of model parameters that can be easily extracted from simple static I-V and C-V measurements. The models are used in a buck-boost bidirectional dc-dc converter, with and without an antiparallel Schottky diode. The efficiency of the converter was analyzed for synchronous and nonsynchronous operation of the switches. An optimal selection of the antiparallel Schottky diode is proposed to minimize the cost of the converter without compromising its efficiency.

Ultrasound influence on I–V–T characteristics of silicon Schottky barrier structure

The influence of ultrasonic loading on current-voltage characteristics has been investigated in Mo/n–n+–Si structures in the temperature range from 130 to 330 K. The longitudinal ultrasonic waves were of 8.4 MHz in frequency and had the intensity approaching 0.3 W/cm2. The acoustically induced reversible modification of the ideality factor and the Schottky barrier height was observed. The temperature dependence of the ultrasound effect was found to be non-monotonic and the parameters variation decreased with the temperature increase from 200 to 330 K. The obtained results have been analyzed on account of the inhomogeneous Schottky barrier model. The ultrasonic loading has been shown to increase the effective density of patches, the barrier height of the uniform region and the patches region and to broaden the patch parameter distribution.

Analytical study of the minority carrier distribution and photocurrent of a Schottky-barrier silicon solar cell

ABSTRACT: Schottky-barrier solar cells have been studied previously by various research workers. In this paper, the excess minority carrier distribution and the photocurrent of Schottky-barrier solar cell have been studied analytically and their dependence of doping concentration and back surface recombination velocity has been reported. An attempt has been made to give an interpretation of the results obtained from theoretical considerations. Normal 0 false false false EN-IN X-NONE X-NONE

Performance Analysis of Rectenna Using Closed Form Equation

Electromagnetics has an important role in power and energy industry. In this paper, the concept of rectenna is introduced firstly. The times past of rectenna for wireless energy harvesting and transmission is then reviewed. Finally examples are employed to illustrate some rectenna design and measurement issues such as rectenna impedance matching and its conversion efficiency. It isalso shown that rectennas can harvest wireless energy efficiently under certain conditions and have the potential to become a power supplier for some special applications. A high-efficiency rectenna component has been calculated and experienced at 6.2 GHz planned for applications involving microwavepower show. The dipole mast and filtering circuitry are printed on a thin duroid substrate. A silicon Schottky barrier mixer diode with a low fail voltage is used as the rectifying device. The rectenna component is tested inside a waveguide simulator and achieves an RF-to-dc conversion efficiency of 85% at an input power level of 55-mW and 347-load. Closed-form equations be agreed meant for the diode efficiency and effort impedance as a sense of payment RF power. Measured in addition to intended efficiency results are in first-class agreement. The mast and circuit design are base on a full-wave electromagnetic simulator. Next harmonic power levels are 19 dB down from the primary input power.

Simulations about self-absorption of tritium in titanium tritide and the energy deposition in a silicon Schottky barrier diode

Simulations on the self-absorption of tritium electrons in titanium tritide films and the energy deposition in a silicon Schottky barrier diode are carried out using the Geant4 radiation transport toolkit. Energy consumed in each part of the Schottky radiovoltaic battery is simulated to give a clue about how to make the battery work better. The power and energy-conversion efficiency of the tritium silicon Schottky radiovoltaic battery in an optimized design are simulated. Good consistency with experiments is obtained.

Characterization of carbon nanotube film-silicon Schottky barrier photodetectors

The authors fabricate vertical geometry single-walled carbon nanotube (CNT) film/p-type silicon Schottky barrier photodetectors, where the CNT film acts as the transparent metal and silicon as the active semiconductor. The authors experimentally characterize the current-voltage, spectral responsivity, and noise properties of these devices under reverse bias. The authors find that the CNT film–Si Schottky barrier photodetectors exhibit a large photocurrent-to-dark current ratio with responsivity as high as 0.10 A/W due to the high transmittance of the CNT film. The measured current noise spectral density shows a 1/f limited behavior and scales as the square of the reverse bias current. The noise equivalent power of the devices is found to be 1.4 × 10−10 W. A comparison between CNT film devices and devices based on conventional metal electrodes is also carried out. These results provide important insights into the properties and performance of CNT film–Si Schottky barrier photodetectors.

Direct Probing of Schottky Barriers in Si Nanowire Schottky Barrier Field Effect Transistors

This work elucidates the role of the Schottky junction in the electronic transport of nanometer-scale transistors. In the example of Schottky barrier silicon nanowire field effect transistors, an electrical scanning probe technique is applied to examine the charge transport effects of a nanometer-scale local top gate during operation. The results prove experimentally that Schottky barriers control the charge carrier transport in these devices. In addition, a proof of concept for a reprogrammable nonvolatile memory device based on band bending at the Schottky barriers will be shown.

First investigations of a silicon neutron detector with a carborane converter

We present a new design of a slow neutron detector, based on silicon detectors with innovative materials acting as conversion layers, plus preliminary results that will be the basis for a more complete study in the near future. The sensitive element of this detector is a Schottky barrier silicon diode covered with o-carborane, a novel boron-based converter material that detects neutrons by means of the 10B(n,α)7Li reaction. This sensor has been simulated with the MCNPX Monte-Carlo software in order to find the optimal converter layer thickness that maximizes the neutron detection efficiency. The simulated maximum efficiency is 2.7% for a 20 μm converter layer of the o-carborane fabricated with pure 10B and of 0.5% for the same compound but made with natural boron material. Moreover, the performance of test devices has been investigated by means of an 241AmBe neutron source and the results have been analyzed with the help of GEANT4 simulations.