• Journal of the Korean Institute of Telematics and Electronics
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• v.25 no.2
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• pp.196-203
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• 1988

A new analytic model for small-singnal circuit model of GaAs MESFET's is presented. This model is a charge model which considers the formation of a statioanary Gunn-domain and the transistion region that exists in the depletion region boundary. From this charge model the analytic expression of the equivalent circuit elements is derived, and the voltage dependences of each element are explained. The results of the calcualtion are in good agreement with experimental data.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.4
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• pp.547-554
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• 1990

Considering channel length modulation, we proposed a GaAs MESFET model for circuit simulator. In existing M.S. Shur's model, two different models are used according to pinch-off voltage of devices. One model for both type of devices was proposed. In this model we introduced weighted switching function(WSF) based on channel length modulation. This proposed model showed better accuracy comparing with existing single law model and complete velocity saturation model.

• Proceedings of the KIEE Conference
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• 2005.10a
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• pp.165-168
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• 2005

In this paper, we examined channel charge which occurs in electron accumulation after electron velocity saturation. Generally, short gate GaAs MESFET show, saturated electron velocity leading to current satulation. When electron velocity is saturated, deletion layer is still open channel and it plays a key role in deciding saturation current mode we proposed channel charge model in channel after electron velocity saturation.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.30B no.7
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• pp.42-49
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• 1993

In this paper, switched-capacitor building block presented which are suitable for implementation in GaAs MESFET technology. They include a current source, a gain stage, and an operational amplifier. Switched-capacitor design techniques are discussed that minimize filter sentsitivity to finite gain of the GaAs operational amplifier. Simulation results are presented on third-order elliptic lowpass ladder filter at a sampling rate of 5GHz.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.2 no.2
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• pp.30-37
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• 1991

The modified method which determines the extrinsic parameters at the small signal equivalent model for GaAs MESFET is presented. It is important that extrinsic parameters are completely eliminated, in order to calculate exact intrinsic parameters. Extrinsic circuit is established by transmission lines, parasitic inductors and capacitors. After these are extracted by S-parameters, intrinsic parameters are calculated. Especially, frequency dependence of parastic inductance and capacitance is considerally constant.

• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.541-544
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• 1998

A SiGe p-channel MESFET using $\delta-doped$ layers is designed and the considerable enhancement of the current driving capability of the device is observed from the result of simulation. The channel consists of double $\delta-doped$ layers separated by a low-doped spacer which consists of Si and SiGe. A quantum well is formed in the valence band of the Si/SiGe heterojunction and much more holes are accumulated in the SiGe spacer than those in the Si spacer. The saturation current is enhanced by the contribution of the holes inthe spacer. Among the design parameters that affect the performance of the device, the thickness of the SiGe layer and the Ge composition are studied. The thickness of $0~300\AA$ and the Ge composition of 0~30% are investigated, and the saturation current is observed to be increased by 45% compared with a double $\delta-doped$ Si p-channel MESFET.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.3 no.1
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• pp.11-19
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• 1992

To design of Ultra-wideband amplifier, we analyzed the inductor peaking to reduce the capacitance effect of GaAs MESFET in upper frequency edge. And we deduced an optimun inductor peaking element from transfer function of GaAs MESFET small-signal equivalent circut and realized the Feedback Amplifier Module (FAM) having flat gain. We design the imput and output impe dance matching networks by Real-Frequency Method. It show that the gain of designed amplifier has a 6.38dB with gain variation 0.56 at 0.1~12 GHz frequency gand by computer simu-lation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.550-553
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• 2001

In this study, unity current gain frequency f$\_$T/ of GaAs MESFET is predicted with different temperatures up to 400 $^{\circ}C$. Temperature dependence parameters of the device including intrinsic carrier concentration n$\_$i/ effective mass, depletion width are considered to be temperature dependent. Small signal parameters such as gate-source, gate dran capacitances C$\_$gs/ C$\_$gd/ are correlated with transconductance g$\_$m/ to predict the unity current gain frequency. The extrinsic capacitance which plays an important roles in high frequency region has been taken into consideration in evaluating total capacitance by using elliptic integral through the substrate. From the results, f$\_$T/ decreases as the temperature increases due to the increase of small signal capacitances and the mobility degradation. Finally the extrinsic elements of capacitances have been proved to be critical in deciding f$\_$T/ which are originated from the design rule of the device.

• Electrical & Electronic Materials
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• v.6 no.6
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• pp.545-552
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• 1993

단층 금속 Al, Au 게이트 MESFET를 제작하여 열처리에 따른 쇼트키 계면에서의 상호확산 상태와 그에 따른 쇼트키 접촉특성 및 MESFET의 전기적 특성을 조사하였다. Al 및 Au 쇼트키 계면의 상호확산은 as-deposited 상태에서도 나타났으며 열처리 온도가 증가함에 따라 상호확산의 정도는 Au 접촉이 Al 접촉보다 컸다. 특히 Au 접촉에서 Ga의 외부확산이 현저했다 .Al 및 Au 게이트에 있어서 공통적으로 열처리 온도 증가에 따라 포화드레인 전류와 핀치오프 전압은 감소하였고 개방채널 저항은 증가하였으며 변화폭은 Au 게이트가 Al 게이트보다 컸다. Al 및 Au 접촉의 장벽높이는 as-deposited 상태에서 각각 0.70eV, 0.73eV로 페르미 준위는 1/2Eg 근처에 피닝되었다. Al 및 Au 접촉에 있어서 열처리 온도 증가에 따라 장벽높이는 각각 증가, 감소하였으며 이상계수는 각각 감소, 증가하였다. Al 접촉의 경우 열처리를 행함으로서 쇼트키 접촉특성이 개선됨을 확인할 수 있었다.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.12
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• pp.1841-1851
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• 1990

Self-aligned gate GaAs MESFETs using ion beam deposited tungsten applicable to GaAs LSI fabrication process have been fabricated. Silicon implanted samples were annealed using isothermla two step RTA process and conventional one step RTA process. The electrical and physicla characteristics of annealed samples were investigated using Hall and I-V measurements. As results of measurements, activation characteristics of the isothermal two step RTA process are better than those of one step annealed ones. Using the developed processes, GaAs SAFETs (Self-Aligned Gate FET) have been fabricated and electdrical characteirstics are measured. As results, subthreshold currents of SAGFETs are 6x10**-10 A/\ulcorner, that is compatible to conventional MESFET, maximum transconductances of 0.75\ulcorner gate MESFET using one step RTA process and 2\ulcorner gate MESFET using isothermal two step RTA process are 18 mS/mm, 41 mS/mm respectively.