• Applied Science and Convergence Technology
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• 제23권3호
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• pp.128-133
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• 2014

We study the ballistic spin transport properties in a two-dimensional electron gas system in the presence of magnetic barriers using a transfer matrix method. We concentrate on the size-effect of the magnetic barriers parallel to a two-dimensional electron gas plane. We calculate the transmission probability of the ballistic spin transport in the magnetic barrier structure while varying the width of the magnetic barriers. It is shown that resonant tunneling oscillation is affected by the width and height of the magnetic barriers sensitively as well as by the inter-spacing of the barriers. We also consider the effect of additional electrostatic modulation on the top of the magnetic barriers, which could enhance the current spin polarization. Because all-semiconductor-based devices are free from the resistance mismatch problem, a resonant tunneling structure using the two-dimensional electron gas system with electric-magnetic modulation would play an important role in future spintronics applications. From the results here, we provide information on the physical parameters of a device to produce well-defined spin-polarized current.

• JSTS:Journal of Semiconductor Technology and Science
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• 제16권2호
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• pp.172-178
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• 2016

In this paper, we propose a sub-10 nm Ge/GaAs heterojunction-based tunneling field-effect transistor (TFET) with vertical band-to-band tunneling (BBT) operation for ultra-low-power (LP) applications. We design a stack structure that is based on the Ge/GaAs heterojunction to realize the vertical BBT operation. The use of vertical BBT operations in devices results in excellent subthreshold characteristics with a reduction in the drain-induced barrier thinning (DIBT) phenomenon. The proposed device with a channel length ($L_{ch}$) of 5 nm exhibits outstanding LP performance with a subthreshold swing (S) of 29.1 mV/dec and an off-state current ($I_{off}$) of $1.12{\times}10^{-11}A/{\mu}m$. In addition, the use of the highk spacer dielectric $HfO_2$ improves the on-state current ($I_{on}$) with an intrinsic delay time (${\tau}$) because of a higher fringing field. We demonstrate a sub-10 nm LP switching device that realizes a good S and lower $I_{off}$ at a lower supply voltage ($V_{DD}$) of 0.2 V.

• 한국자기학회지
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• 제3권1호
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• pp.29-33
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• 1993

$1{\times}10^{-6}$Torr의 진공에서 열저항 가열식 진공증착 방법으로 제작한 $Permalloy/Al_{2}O_{3}/Co$ 강자성 터널집합의 자기저항 효과를 조사하였다. 이 논문에서는 제작한 강자성 터널접합 시료의 전류-전압 특성과 자기 valve 효과를 측정하고, 시료진동형자기계로 측 정한 자기이력곡선을 통하여 터널저항의 히스테리시스성 자장 의존성을 조사하였다. 터널링은 전류-전압 특성을 측정함으로써 확인 되어진다. 자기저항의 히스테리시스 곡선은 자화의 히스테 리시스 곡선과 잘 대응한다. 측정한 자기저항비 ${\Delta}R/R$은 실온에서 약 0.6% 였다.

• 한국전기전자재료학회논문지
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• 제14권11호
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• pp.934-940
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• 2001

Magnetic properties were investigated for Si/SiO$_2$/NiFe(300 )/A1$_2$O$_3$(t)/Co(200 ) junction related with the parameters of $Al_2$O$_3$. Insulating $Al_2$O$_3$ layer was formed by depositing a 5~40 thick Al layer, followed by a 90~120s RF plasma oxidation in an $O_2$ atmosphere. Magnetoresistance was not observed for tunnel junction with 5~10 thick Al layer, but magnetoresistance was observed large for tunnel junction with 15~40 thick Al layer. Oxidation time did not largely influence magnetoresistance. Tunnel magnetoresistance effect depended on magnetization behavior of two ferromagnetic layers. Tunneling junction was confirmed through nonlinear I-V curve. In this work, tunneling magnetoresistance(TMR) up to 30 % was observed. This apparent TMR is an artifact of the nonuniform current flow over the junction in the cross geometry of the electrodes.

• Journal of Electrical Engineering and Technology
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• 제9권5호
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• pp.1654-1659
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• 2014

Tunneling field-effect transistors (TFETs) are very applicable to low standby-power application by their virtues of low off-current ($I_{off}$) and small subthreshold swing (S). However, low on-current ($I_{on}$) of silicon-based TFETs has been pointed out as a drawback. To improve $I_{on}$ of TFET, a gate-all-around (GAA) TFET based on III-V compound semiconductor with InAs/InGaAs/InP multiple-heterojunction structure is proposed and investigated. Its performances have been evaluated with the gallium (Ga) composition (x) for $In_{1-x}Ga_xAs$ in the channel region. According to the simulation results for $I_{on}$, $I_{off}$, S, and on/off current ratio ($I_{on}/I_{off}$), the device adopting $In_{0.53}Ga_{0.47}As$ channel showed the optimum direct-current (DC) performance, as a result of controlling the Ga fraction. By introducing an n-type InGaAs thin layer near the source end, improved DC characteristics and radio-frequency (RF) performances were obtained due to boosted band-to-band (BTB) tunneling efficiency.

• 센서학회지
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• 제26권2호
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• pp.79-84
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• 2017

The drain current of the SB MOSFET was analytically modeled by an equation composed of thermionic emission and tunneling with consideration of the image force lowering. The depletion region electron concentration was used to model the channel electron concentration for the tunneling current. The Schottky barrier width is dependent on the channel electron concentration. The drain current is changed by the gate oxide thickness and Schottky barrier height, but it is hardly changed by the doping concentration. For a GaN SB MOSFET with ITO source and drain electrodes, the calculated threshold voltage was 3.5 V which was similar to the measured value of 3.75 V and the calculated drain current was 1.2 times higher than the measured.

• 비파괴검사학회지
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• 제28권6호
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• pp.524-530
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• 2008

The spin valve tunneling magnetoresistance (SV-TMR) sensor performance is analyzed using Stoner-Wohlfarth model for the detection of eddy current signals in nondestructive testing applications. The SV-TMR response in terms of the applied AC magnetic field dominantly generates the second harmonic amplitude in hard axis direction. The second harmonic eddy current signal detection using SV-TMR sensor shows higher performance than that of the coil sensor at lower frequencies. The SV-TMR sensor with high sensitivity gives a good solution to improve the low frequency performance in comparison with the inductive coil sensors. Therefore, the low frequency eddy current techniques based on SV-TMR sensors are specially useful in the detection of hidden defects, and it can be applied to detect the deeply embedded flaws or discontinuities in the conductive materials.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집
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• pp.198-201
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• 2002

We have studied the temperature dependence of current-voltage and luminance-voltage characteristics of Organic Light Emitting Diodes(OLEDs). The OLEDS are based on the molecular compounds, N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine (TPD) as a hole transport, tris(8-hydroxyquinolinoline) aluminum(III) (Alq$_3$) as an electron transport, and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as a buffer layer. The current-voltage and luminance-voltage characteristics were measured in the temperature range of 10[K] and 300[K]. A conduction mechanism in OLEDs has been interpreted in terms of space-charge-limited current(SCLC) and tunneling mechanism.

• JSTS:Journal of Semiconductor Technology and Science
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• 제13권6호
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• pp.546-550
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• 2013

We propose a novel negative differential resistance (NDR) device with ultra-high peak-to-valley current ratio (PVCR) by combining pn junction diode with depletion mode nanowire (NW) transistor, which suppress the valley current with transistor off-leakage level. Band-to-band tunneling (BTBT) Esaki diode with degenerately doped pn junction can provide multiple switching behavior having multi-peak and valley currents. These multiple NDR characteristics can be controlled by doping concentration of tunnel diode and threshold voltage of NW transistor. By designing our NDR device, PVCR can be over $10^4$ at low operation voltage of 0.5 V in a single peak and valley current.

• E2M - 전기 전자와 첨단 소재
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• 제10권1호
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• pp.26-32
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• 1997

The gate induced drain leakage(GIDL) current under the stress of worse case in -MOSFET's with ultrathin gate oxides has been measured and characterized. The GIDL current was shown that P-MOSFET's of the thicker gate oxide is smaller than that of the thinner gate oxide. It was the results that the this cur-rent is decreased with the increamental stress time at the same devices.It is analyzed that the formation components of GIDL current are both energy band to band tunneling at high gate-drain voltage and energy band to defect tunneling at low drain-gate voltage. The degradations of GIDL current was analyzed the mechanism of major role in the hot carriers trapping in gate oxide by on-state stress.