• 대한전자공학회논문지SD
• /
• 제42권5호
• /
• pp.9-14
• /
• 2005

본 논문은 순수한 고주파 (radio-frequency: rf) 모드의 반사형과 투과형 고주파 단일전자 트랜지스터 (RF-SET) 동작의 새로운 시뮬레이션 기법을 소개한다. 이 기법은 RF-SET 회로를 주파수 영역에서 self-consistent 방법으로 키리히호프 법칙에 기반한 미분 방정식의 해를 구한다. 또한, 이 기법은 정상상태와 시변 단일전자 트랜지스터 전류 모델들 두 가지를 포함한다. 순수한 rf 모드 반사형 RF-SET의 반사파와 순수한 rf 모드 투과형 RF-SET의 투과파를 계산한다. 정상상태 단일전자 트랜지스터 전류 모델을 포함한 RF-SET 계산의 정확성은 [참고문헌 2]에서 소개된 방법으로 확인한다. GHz 이상의 고주파에서 시변 단일전자 트랜지스터 전류 모델을 포함한 RF-SET 계산 결과는 정상상태 단일전자 트랜지스터 전류 모델을 포함해서 RF-SET를 계산한 결과들과 상당한 차이가 있음을 확인했다. GHz 이상 고주파에서 RF-SET 동작 분석은 정확한 시변 단일전자 트랜지스터의 전류 모델이 요구된다.

• JSTS:Journal of Semiconductor Technology and Science
• /
• 제16권2호
• /
• pp.185-190
• /
• 2016

A 70-${\AA}$ nanowire field-effect transistor (FET) for sub-10-nm CMOS technology is designed and simulated in order to investigate the impact of an oxide trap on random telegraph noise (RTN) in the device. It is observed that the drain current fluctuation (${\Delta}I_D/I_D$) increases up to a maximum of 78 % due to the single electron trapping. In addition, the effect of various trap positions on the RTN in the nanowire FET is thoroughly analyzed at various drain and gate voltages. As the drain voltage increases, the peak point for the ${\Delta}I_D/I_D$ shifts toward the source side. The distortion in the electron carrier density and the conduction band energy when the trap is filled with an electron at various positions in the device supports these results.

• 대한전기학회논문지:전기물성ㆍ응용부문C
• /
• 제49권10호
• /
• pp.564-569
• /
• 2000

This paper analyzed single AlGaAs/GaAa heterojunction energy band structures by solving Schr dinger's equation and Poisson's equation self-consistently. Four different concentrations, positively ionized donors, holes in the valence band, free electrons in the conduction band and 2DEG are taken into account for the whole system. 2DEG from both of the structures are obtained and compared with the date available in the literatures. Differential capacitances are also calculated from the concentration profiles obtained to prove the validity of the single AlGaAs/GaAs system. Finally, theoretical predictions for both of 2DEGs and the capacitances show good agreement with the experimental data referred in this study. It has only an error of les than 10 percent.

• International Journal of Precision Engineering and Manufacturing
• /
• 제7권1호
• /
• pp.42-46
• /
• 2006

This paper presents a method for deposition an individual carbon nanotube (CNT). The alignment of a single CNT is very useful to perform studies related to applications in FET (Field Emitted Transistor), SET (Single Electron Transistor) and to make chemical sensor as well as bio sensors. In this study, we developed the deposition method of a CNT individualized in a solution. Using the electrokinetic method, we found the optimum conditions to assemble the nanotube and discussed about plausible explanation for the assembling mechanism. These results will be available to use for making the CNT sensor device.

• 대한전자공학회논문지SD
• /
• 제40권4호
• /
• pp.1-12
• /
• 2003

본 논문에서는 과도상태 회로 시뮬레이션에서 각각의 단일전자 트랜지스터 (Single electron transistor: SET)가 독립적으로 다루어질 수 있는 영역을 체계적으로 조사했다. Interconnection 정전용량이 충분히 큰 회로의 과도상태 시뮬레이션에서도 정상상태 경우와 마찬가지로 각각의 SET가 독립적으로 다뤄질 수 있음을 찾았다. 그러나, 각각의 SET들이 서로 독립적으로 다뤄질 수 있는 interconnection의 부하정전용량은 정상상태보다 약 10배 정도 크다. 이런 조건에서 SPICE에 적용 가능한 단일전자 트랜지스터 (Single electron transistor: SET)의 과도상태 compact 모델을 제시한다. 이 모델은 SPICE main routine의 admittance 행렬과 전류 행렬 구성 요소를 효율적으로 만들기 위해 새롭게 개발된 등가회로 접근방식에 기초한다. 과도상태 모델은 전자우물 안의 전자 개수를 정확히 계산하기 위해서 시변 master 방정식 solver를 각각 포함한다. 이 모델을 이용해서 단일전자 회로 및 단일전자 소자/회로와 CMOS 회로가 결합한 SET/CMOS hybrid 회로를 성공적으로 계산했다. SPICE에 적용된 기존의 시뮬레이터의 결과와 비교해서 상당히 일치하며 CPU 계산 시간도 더 짧아짐을 보인다.

• JSTS:Journal of Semiconductor Technology and Science
• /
• 제6권1호
• /
• pp.52-58
• /
• 2006

Single-electron transistor (SET)-based logic cells and SET/FET hybrid integrated circuits have been fabricated on SOI chips. The input-output voltage transfer characteristic of the SET-based complementary logic cell shows an inverting behavior where the output voltage gain is estimated to be about 1.2 at 4.2K. The SET/FET output driver, consisting of one SET and three FETs, yields a high voltage gain of 13 and power amplification with a wide-range output window for driving next circuit. Finally, the SET/FET literal gate for a multi-valued logic cell, comprising of an SET, an FET and a constant-current load, displays a periodic voltage output of high/low level multiple switching with a swing as high as 200mV. The multiple switching functionality of all the fabricated logic circuits could be enhanced by utilizing a side gate incorporated to each SET component to enable the phase control of Coulomb oscillations, which is one of the unique characteristics of the SET-based logic circuits.

• Journal of Magnetics
• /
• 제7권1호
• /
• pp.4-8
• /
• 2002

The magnetoresistance (MR) and the magnetization reversal of a lateral spin-injection device based on a spin-polarized field effect transistor (spin FET) have been investigated. The device consists of a two-dimensional electron gas (2DEG) system in an InAs single quantum well (SQW) and two ferromagnetic $(Ni_{80}Fe_{20})$ contacts: all injector (source) and a detector (drain). Spin-polarized electrons are injected from the first contact and, after propagating through the InAs SQW are collected by the second contact. By engineering the shape of the permalloy contacts, we were able to observe distinct switching fields $(H_c)$ from the injector and the collector by using scanning Kerr microscopy and MR measurements. Magneto-optic Kerr effect (MOKE) hysteresis loops demonstrate that there is a range of magnetic field (20~60 Oe), at room temperature, over which the magnetization in one contact is aligned antiparallel to that in the other. The MOKE results are consistent with the variation of the magnetoresistance in the spin-injection device.

• 한국자기학회:학술대회 개요집
• /
• 한국자기학회 2003년도 하계학술연구발표회 및 한.일 공동심포지엄
• /
• pp.24-24
• /
• 2003

Metallic magnetoelectronic devices have studied intensively and extensively for last decade because of the scientific interest as well as great technological importance. Recently, the scientific activity in spintronics field is extending to the hybrid devices using ferromagnetic/semiconductor heterostructures and to new ferromagnetic semiconductor materials for future devices. In case of the hybrid device, conductivity mismatch problem for metal/semiconductor interface will be able to circumvent when the device operates in ballistic regime. In this respect, spin-valve transistor, first reported by Monsma, is based on spin dependent transport of hot electrons rather than electron near the Fermi energy. Although the spin-valve transistor showed large magnetocurrent ratio more than 300%, but low transfer ratio of the order of 10$\^$-5/ prevents the potential applications. In order to enhance the collector current, we have prepared magnetic tunneling transistor (MTT) with single ferromagnetic base on Si(100) collector by magnetron sputtering process. We have changed the resistance of tunneling emitter and the thickness of baser layer in the MTT structure to increase collector current. The high transfer ratio of 10$\^$-4/ range at bias voltage of more than 1.8 V, collector current of near l ${\mu}$A, and magnetocurrent ratio or 55% in Si-based MTT are obtained at 77K. These results suggest a promising candidate for future spintronic applications.

• Advances in nano research
• /
• 제12권1호
• /
• pp.25-35
• /
• 2022

Within the framework of the density functional theory combined with the method of non-equilibrium Green's functions (DFT + NEGF), the features of electron transport in fullerene nanojunctions, which are «core-shell» nanoobjects made of a combination of fullerenes of different diameters C₂₀, C₈₀, C₁₈₀, placed between gold electrodes (in a nanogap), are studied. Their transmission spectra, the density of state, current-voltage characteristics and differential conductivity are determined. It was shown that in the energy range of -0.45-0.45 eV in the transmission spectrum of the "Au-C₁₈₀-Au" nanojunction appears a HOMO-LUMO gap with a width of 0.9 eV; when small-sized fullerenes C₂₀, C₈₀ are intercalation into the cavity C₁₈₀ the gap disappears, and a series of resonant structures are observed on their spectra. It has been established that distinct Coulomb steps appear on the current-voltage characteristics of the "Au-C₁₈₀-Au" nanojunction, but on the current-voltage characteristics "Au-C₈₀@C₁₈₀-Au", "Au-(C₂₀@C₈₀)@C₁₈₀-Au" these step structures are blurred due to a decrease in Coulomb energy. An increase in the number of Coulomb features on the dI/dV spectra of core-shell fullerene nanojunctions was revealed in comparison with nanojunctions based on fullerene C₆₀, which makes it possible to create high-speed single-electron devices on their basis. Models of single-electron transistors (SET) based on fullerene nanojunctions "Au-C₁₈₀-Au", "Au-C₈₀@C₁₈₀-Au" and "Au-(C₂₀@C₈₀)@C₁₈₀-Au" are considered. Their charge stability diagrams are analyzed and it is shown that SET based on C₈₀@C₁₈₀-, (C₂₀@C₈₀)@C₁₈₀- nanojunctions is output from the Coulomb blockade mode with the lowest drain-to-source voltage.

• 센서학회지
• /
• 제14권5호
• /
• pp.331-336
• /
• 2005

The influence of water molecule on the electrical properties of single-walled carbon nanotube field effect transistors (SWNT-FETs) was reported. Conductance suppression was observed with the increase of the humidity. This can be explained by doping of the SWNT-FETs, which has p-type semiconductor characteristic, with the water molecules acting as an electron donor. However, after 65 % of humidity, conductance of the SWNT-FETs started to increase again, due to the opening of electron channels. Upon annealing at $400^{\circ}C$ in Ar atmosphere, conductance increases more than 500 %, and the threshold voltage shifts toward further positive gate voltages. The results of this experiment support possible application of single-walled carbon nanotubes for humidity sensing material.