• JSTS:Journal of Semiconductor Technology and Science
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• v.10 no.2
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• pp.152-159
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• 2010

We propose a semi-analytical current conduction model for depletion-mode n-type nanowire field-effect transistors (NWFETs) with top-gate structure. The NWFET model is based on an equivalent circuit consisting of two back-to-back Schottky diodes for the metal-semiconductor (MS) contacts and the intrinsic top-gate NWFET. The intrinsic top-gate NWFET model is derived from the current conduction mechanisms due to bulk charges through the center neutral region as well as of accumulation charges through the surface accumulation region, based on the electrostatic method, and thus it includes all current conduction mechanisms of the NWFET operating at various top-gate bias conditions. Our previously developed Schottky diode model is used for the MS contacts. The newly developed model is integrated into ADS, in which the intrinsic part of the NWFET is developed by utilizing the Symbolically Defined Device (SDD) for an equation-based nonlinear model. The results simulated from the newly developed NWFET model reproduce considerably well the reported experimental results.

• Journal of the Korean Institute of Telematics and Electronics
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• v.20 no.3
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• pp.33-39
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• 1983

New Schottky devices with thin stepped oxide layer (about 1000 ${\AA}$) along the edge of metal-semiconductor junction have been designed and fabricated. The breakdown voltages of these diodes have been compared with those of conventional metal overlap and P guard ring Schottky diode structures. Thin stepped oxide layer has been grown by the process of T.C.E. oxidation. In order to compare and demonstrate the improved down phenomena of these devices, conventional metal overlap diode and P guard ring which have the same dimension with new devices have also been integrated in a same New Schottty devices structured with thin stepped oxide layer have shown significant improvement in breakdown phenomena compared with conventional diodes.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.305-305
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• 2010

It is known that a pulse of electrons of high kinetic energy (1-3 eV) in metals can be generated with the deposition of external energy to the surface such as in the absorption of light or in exothermic chemical processes. These energetic electrons are not in thermal equilibrium with the metal atoms and are called "hot electrons" The concept of photon energy conversion to hot electron flow was suggested by Eric McFarland and Tang who directly measured the photocurrent on gold thin film of metal-semiconductor ($TiO_2$) Schottky diodes [1]. In order to utilize this scheme, we have fabricated metal-semiconductor Schottky diodes that are made of Pt or Au as a metallic layer, Si or $TiO_2$ as a semiconducting substrate. The Pt/$TiO_2$ and Pt/Si Schottky diodes are made by PECVD (Plasma Enhanced Chemical Vapor Deposition) for $SiO_2$, magnetron sputtering process for $TiO_2$, e-beam evaporation for metallic layers. Metal shadow mask is made for device alignment in device fabrication process. We measured photocurrent on Pt/n-Si diodes under AM1.5G. The incident photon to current conversion efficiency (IPCE) at different wavelengths was measured on the diodes. We also show that the steady-state flow of hot electrons generated from photon absorption can be directly probed with $Pt/TiO_2$ Schottky diodes [2]. We will discuss possible approaches to improve the efficiency of photon energy conversion.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.290.1-290.1
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• 2013

The electrical characterization of Au islands on TiO2 at nanometer scale (as a Schottky nanodiode) has been studied with conductive atomic force microscopy in ultra-high vacuum. The diverse sizes of the Au islands were formed by using self-assembled patterns on n-type TiO2 semiconductor film using the Langmuir-Blodgett process. Local conductance images showing the current flowing through the TiN coated AFM probe to the surface of the Au islands on TiO2 was simultaneously obtained with topography, while a positive sample bias is applied. The boundary of the Au islands revealed a higher current flow than that of the inner Au islands in current AFM images, with the forward bias presumably due to the surface plasmon resonance. The nanoscale Schottky barrier height of the Au/TiO2 Schottky nanodiode was obtained by fitting the I-V curve to the thermionic emission equation. The local resistance of the Au/TiO2 nanodiode appeared to be higher at the larger Au islands than at the smaller islands. The results suggest that conductive atomic force microscopy can be used to reveal the I-V characterization of metal size dependence and the electrical effects of surface plasmon on a metal-semiconductor Schottky diode at nanometer scale.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.48 no.2
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• pp.14-19
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• 2011

We have fabricated GaN Schottky barrier diode (SBD) for high-voltage applications on Si substrate. The leakage current and the electrical characteristics of GaN SBD are investigated by annealing metal-semiconductor junctions. Ohmic junctions of Ti/Al/Mo/Au and Schottky junctions of Ni/Au are used in the fabrication. A test structure is proposed to measured buffer leakage current through a mesa structure. When annealing temperature is increased from $700^{\circ}C$ to $800^{\circ}C$, measured buffer leakage current is also increased from 87 nA to 780 nA at the width of 100 ${\mu}m$. The diffusion of Au, Ti, Mo, O into GaN buffer layer increases the leakage current and that is verified by Auger electron spectroscopy. Experimental results show that the low leakage current and the high breakdown voltage of GaN SBD are achieved by annealing metal-semiconductor junctions.

• Advances in nano research
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• v.10 no.4
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• pp.339-347
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• 2021

In the framework of the density functional theory combined with the method of non-equilibrium Green functions (DFT + NEGF), the electric transport properties of a one-dimensional nanodevice consisting of telescoping polyprismanes with various types of electrical conductivity were studied. Its transmission spectra, density of state, current-voltage characteristic, and differential conductivity are determined. It was shown that C_[14,17], C_[14,11], C_[14,16], C_[14,10] show a metallic nature, and polyprismanes C_[14,5], C_[14,4] possess semiconductor properties and has a band gap of 0.4 eV and 0.6 eV, respectively. It was found that, when metal C_[14,11], C_[14,10] and semiconductor C_[14,5], C_[14,4] polyprismanes are coaxially connected, a Schottky barrier is formed and a weak diode effect is observed, i.e., manifested valve (rectifying) property of telescoping polyprismanes. The enhancement of this effect occurs in the nanodevices C_[14,17] - C_[14,11] - C_[14,5] and C_[14,16] - C_[14,10] - C_[14,4], which have the properties of nanodiode and back nanodiode, respectively. The simulation results can be useful in creating promising active one-dimensional elements of nanoelectronics.

• Advances in nano research
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• v.10 no.5
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• pp.471-479
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• 2021

In the framework of the density functional theory combined with the method of non-equilibrium Green functions (DFT + NEGF), the electric transport properties of a one-dimensional nanodevice consisting of telescoping polyprismanes with various types of electrical conductivity were studied. Its transmission spectra, density of state, current-voltage characteristic, and differential conductivity are determined. It was shown that C_[14,17], C_[14,11], C_[14,16], C_[14,10] show a metallic nature, and polyprismanes C_[14,5], C_[14,4] possess semiconductor properties and has a band gap of 0.4 eV and 0.6 eV, respectively. It was found that, when metal C_[14,11], C_[14,10] and semiconductor C_[14,5], C_[14,4] polyprismanes are coaxially connected, a Schottky barrier is formed and a weak diode effect is observed, i.e., manifested valve (rectifying) property of telescoping polyprismanes. The enhancement of this effect occurs in the nanodevices C_[14,17] - C_[14,11] - C_[14,5] and C_[14,16] - C_[14,10] - C_[14,4], which have the properties of nanodiode and back nanodiode, respectively. The simulation results can be useful in creating promising active one-dimensional elements of nanoelectronics.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.12
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• pp.56-63
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• 1994

The effects of sulfur treatments on the barrier heithts of Schottky contacts and the interface-state density of metal-insulator-semiconductor (MIS) capacitors on InP have been investigated. Schottky contacts were formed by the evaporation of Al, Au, and Pt on n-InP substrate before and after (NH$_{4}$)$_{2}$S$_{x}$ treatments, respectively. The barrier height of InP Schottky contacts was measured by their current-voltage (I-V) and capacitance-voltage (C_V) characteristics. We observed that the barrier heights of Schottky contacks on bare InP were 0.35~0.45 eV nearly independent of the metal work function, which is known to be due to the surface Fermi level pinning. In the case of sulfur-treated Au/InP ar Pt/InP Schottky diodes, However, the barrier heights were not only increased above 0.7 eV but also highly dependent on the metal work function. We have also investigated effects of (NH$_{4}$)$_{2}$S$_{x}$ treatments on the distribution of interface states in Si$_{3}$N$_{4}$InP MIS diodes where Si$_{3}$N$_{4}$ was provided by plasma enhanced chemical vapor deposition (PECVD). The typical value of interface-state density extracted feom 1 MHz C-V curve of sulfur-treated SiN$_{x}$/InP MIS diodes was found to be the order of 5${\times}10^{10}cm^{2}eV^{1}$. This value is much lower than that of MiS diodes made on bare InP surface. It is certain, therefore, that the (NH$_{4}$)$_{2}$S$_{x}$ treatment is a very powerful tool to enhance the barrier heights of Au/n-InP and Pt/n-InP Schottky contacts and to reduce the density of interface states in SiN$_{x}$/InP MIS diode.

• ETRI Journal
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• v.30 no.6
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• pp.826-832
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• 2008

The metal-ferroelectric-metal (MFM) capacitor in the ferroelectric random access memory (FeRAM) embedded RFID chip is used in both the memory cell region and the peripheral analog and digital circuit area for capacitance parameter control. The capacitance value of the MFM capacitor is about 30 times larger than that of conventional capacitors, such as the poly-insulator-poly (PIP) capacitor and the metal-insulator-metal (MIM) capacitor. An MFM capacitor directly stacked over the analog and memory circuit region can share the layout area with the circuit region; thus, the chip size can be reduced by about 60%. The energy transformation efficiency using the MFM scheme is higher than that of the PIP scheme in RFID chips. The radio frequency operational signal properties using circuits with MFM capacitors are almost the same as or better than with PIP, MIM, and MOS capacitors. For the default value specification requirement, the default set cell is designed with an additional dummy cell.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.662-662
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• 2013

Over the last several decades, innovative light-harvesting devices have evolved to achieve high efficiency in solar energy transfer. Research on the mechanisms for plasmon resonance is very desirable to overcome the conventional efficiency limits of photovoltaics. The influence of localized surface plasmon resonance on hot electron flow at a metal-semiconductor interface was observed with a Schottky diode composed of a thin silver layer on $TiO_2$. The photocurrent is generated by absorption of photons when electrons have enough energy to travel over the Schottky barrier and into the titanium oxide conduction band. The correlation between the hot electrons and the surface plasmon is confirmed by matching the range of peaks between the incident photons to current conversion efficiency (IPCE, flux of collected electrons per flux of incident photons) and UV-Vis spectra. The photocurrent measured on Ag/$TiO_2$ exhibited surface plasmon peaks; whereas, in contrast to the Au/$TiO_2$, a continuous Au thin film doesn't exhibit surface plasmon peaks. We modified the thickness and morphology of a continuous Ag layer by electron beam evaporation deposition and heating under gas conditions and found that the morphological change and thickness of the Ag film are key factors in controlling the peak position of light absorption.