• E2M - 전기 전자와 첨단 소재
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• 제11권10호
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• pp.60-65
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• 1998

Deposition conditions, surface morphology, and electrical properties of polyamic acid alkylamine salts (PAAS) Langmuir-Blodgett(LB) films have been investigated through a study of surface pressure-area $\pi$-A isotherms, AFM (atomic force microscopy), and current-voltage characteristics. To obtain the optimum conditions of film deposition, the $\pi$-A isotherms were examined by varying temperature, barrier moving speed, dipping speed, spreading amount of solution etc. The Z-type LB films were made at the surface pressure of 5 mN m-1 and 25 mN m-1 for the AFM study; the former surface pressure forms the gas phase and the latter one forms the solid phase. The LB film made in the gas phase show domains with a size of about 200 A diameter and 70 A height. However, the LB films made in the solid phase show a very smooth surface with 2 A surface roughness. In the current-voltage characteristics measured along the perpendicular direction of the films, ohmic conduction has been observed below 105 V cm-1 and the calculated electrical conductivity is about 10-13 S cm-1. Nonohmic conduction has been observed above = 10-11 V cm and the conduction mechanism can be explained by the Schottky effect.

• JSTS:Journal of Semiconductor Technology and Science
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• 제3권2호
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• pp.96-101
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• 2003

Direct evidence on the incorporation of high concentration of oxygen into undoped AlGaN layers for the AlGaN/GaN heterostuctures is provided by scanning photoemission microscopy using synchrotron radiation. In-situ annealing at $1000^{\circ}C$ resulted in a significant increase in the oxygen concentration at the AlGaN surface due to the predominant formation of Al-O bonds. The oxygen incorporation into the AlGaN layers resulting from the high reactivity of Al to oxygen can enhance the tunneling-assisted transport of electrons at the metal/AlGaN interface, leading to the reduction of the Schottky barrier height and the increase of the sheet carrier concentration near the AlGaN/GaN interface.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.1270-1271
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• 2008

Effects of thin ZnO/Mg interlayers on electrical and optical properties between p-GaN and ITO were characterized for its application to GaN-LEDs. The ZnO and Mg layers were deposited to have various thicknesses (1${\sim}$6nm for ZnO and 1${\sim}$2nm for Mg) by sputtering. After RTA process, the atomic migration between Mg and ZnO and the formation of Ga vacancy were observed from SIMS depth profile, resulting in the increase of hole concentration and the reduction of band bending at the surface region of p-GaN. The sample using ZnO(2nm)/Mg(2nm) interlayer produced the lowest contact resistance with SBH(Schottky barrier height) of 0.576 eV and the transmittance higher than 83% at a wavelength of 460nm when annealed at 500$^{\circ}C$ for 3min in air ambient.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.132-132
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• 2008

Silicon carbide (SiC) is an attractive material for high-power, high-temperature, and high-frequency applications. So far, atomic force microscopy (AFM) has been extensively used to study the surface charges, dielectric constants and electrical potential distribution as well as topography in silicon-based device structures, whereas it has rarely been applied to SiC-based structures. In this work, the surface potential and topography distributions SiC with different doping levels were measured at a nanometer-scale resolution using a scanning kelvin probe force microscopy (SKPM) with a non-contact mode AFM. The measured results were calibrated using a Pt-coated tip and a metal defined electrical contacts of Au onto SiC. It is assumed that the atomically resolved surface potential difference does not originate from the intrinsic work function of the materials but reflects the local electron density on the surface. It was found that the work function of the Au deposited on SiC surface was higher than that of original SiC surface. The dependence of the surface potential on the doping levels in SiC, as well as the variation of surface potential with respect to the schottky barrier height has been investigated. The results confirm the concept of the work function and the barrier heights of metal/SiC structures.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 하계종합학술대회 논문집(2)
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• pp.310-313
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• 2000

In this study, the Au/Ni and Au/Ni/Si/Ni layers prepared by electron beam evaporation were used to form ohmic contacts on p-type GaN. Before rapid thermal annealing, the current-voltage(I-V) characteristic of Au/Ni and Au/Ni/Si/Ni contact on p-type GaN film shows non-ohmic behavior. A Specific contact resistance as 3.4$\times$10$^{-4}$ Ω-$\textrm{cm}^2$ was obtained after 45$0^{\circ}C$-RTA. The Schottky barrier height reduction may be attributed to the presence of Ga-Ni and Ga-Au compounds, such as Ga$_4$Ni$_3$, Ga$_4$Ni$_3$, and GaAu$_2$ at the metal - semiconductor interface. The mixing behaviors of both Ni and Au have been studied by using X-ray photoelectron spectroscopy. In addition, X-ray diffraction measurements indicate that the Ni$_3$N, NiGa$_4$, Ni$_2$Si, and Ni$_3$Si$_2$ Compounds were formed at the metal-semiconductor interface.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.150-150
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• 2008

본 연구에서는 Wet chemistry damage가 Nanopatterned p-ohmic electrode에 미치는 영향을 연구하였다. Nanopattern은 Metal clustering을 이용하여, P-GaN와 Ohmic형성에 유리한 Pd을 50$\AA$ 적층한 후 Rapid Thermal Annealing방법으로 $850^{\circ}C$, $N_2$분위기에서 3min열처리를 하여 Pd Clustering mask 를 제작하였다. Wet etching은 $85^{\circ}C$, $H_3PO_4$조건에서 시간에 따라 Sample을 Dipping하는 방법으로 시행하였다 Ohmic test를 위해서 Circular - Transmission line Model 방법을 이용하였으며, Atomic Force Microscopy과 Parameter Analyzer로 Nanopatterned GaN surface위에 형성된 Ni/ Au Contact에서의 전기적 분석과, 표면구조분석을 시행하였다. AFM결과 Wet처리시간에 따라서 Etching형상 및 Etch rate이 영향을 받는 것이 확인되었고, Ohmic test에서 Wet chemistry처리에 의한 Tunneling parameter와 Schottky Barrier Height가 크게 증/감함을 관찰하였다. 이러한 결과들은 Wet처리에 의해서 발생된 Defect가 GaN의 표면과 하부에서 발생되며, Deep acceptor trap 및 transfer거동과 밀접한 관련이 있음을 확인 할 수 있었다. 보다 자세한 Transport 및 Wet chemical처리영향에 관한 형성 Mechanism은 후에 I-V-T, I-V, C-V, AFM결과 들을 활용하여 발표할 예정이다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2010년도 제39회 하계학술대회 초록집
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• pp.171-171
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• 2010

In this work, we investigated the effect of the oxidation temperature on the unipolar and bipolar resistance switching behaviors of the oxidized TiO-x films. TiOx films on Pt electrodes were fabricated by the oxidation of Ti films at $550^{\circ}C$ for 1 to 3 hours. The unipolar and bipolar resistance switching properties were investigated with the oxidation temperature and time. Also, the crystal structure and the physical properties such as chemical bonding states of TiOx layers were characterized in addition to the resistance switching characteristics. The resistance switching behaviors of TiOx films oxidized at above $450^{\circ}C$ and below $650^{\circ}C$ was shown. So, we investigated that the resistance switching behaviors of TiOx films oxidized at $550^{\circ}C$ with the oxidation time from 1 to 3 hour. The memory windows of unipolar switching in the oxidized TiOx films were reduced with increasing the oxidation time, but those of the bipolar switching were slightly enlarged. The enlargement of rutile TiO2 peak with increasing the oxidation time and temperature was studied by X-ray diffraction. An increase of non-lattice oxygen and Ti3+ in the TiOx films with the oxidation times was investigated by X-ray photoemission spectroscopy. It was expected that the uipolar and bipolar resistive switching of the oxidized TiOx film was strongly related with the migration of non-lattice oxygen anions and schottky barrier height, respectively.

• 한국정보통신학회논문지
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• 제3권1호
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• pp.229-234
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• 1999

측정 온도 변화와 n-형 실리콘 기판 농도의 변화를 갖는 백금 쇼트키 다이오드에서 신뢰성 특성을 분석하였다. 신뢰성 측정분석의 파라미터는 순방향 바이어스에서 포화전류, 임계전압과 이상인자이고, 소자의 모양에 따라서 역방향 바이어스에서 항복전압이다. 소자의 모양은 가장자리 효과를 위한 긴직사각형과 정사각형이다. 결과로써, 백금과 엔-실리콘 접합 부분에서 증가된 농도에 의해 순방향 임계전압, 장벽높이와 역방향 항복전압은 감소되었지만 이상인자와 포화전류는 증가되었다. 순방향과 역방향 바이어스 하에서 신뢰성 특성의 추출된 전기적 파라미터 값들은 측정온도(실온,$50^{\circ}C$, $75^{\circ}C$)에서 더 높은 온도에서 증가되었다. 긴직사각형 소자가 가장자리 부분의 터널링 효과에 의해 역방향 항복 특성에서 정사각형 소자보다 감소되었다.

• 한국재료학회지
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• 제34권6호
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• pp.283-290
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• 2024

The aggressive scaling of dynamic random-access memory capacitors has increased the need to maintain high capacitance despite the limited physical thickness of electrodes and dielectrics. This makes it essential to use high-k dielectric materials. TiO₂ has a large dielectric constant, ranging from 30~75 in the anatase phase to 90~170 in rutile phase. However, it has significant leakage current due to low energy barriers for electron conduction, which is a critical drawback. Suppressing the leakage current while scaling to achieve an equivalent oxide thickness (EOT) below 0.5 nm is necessary to control the influence of interlayers on capacitor performance. For this, Pt and Ru, with their high work function, can be used instead of a conventional TiN substrate to increase the Schottky barrier height. Additionally, forming rutile-TiO₂ on RuO₂ with excellent lattice compatibility by epitaxial growth can minimize leakage current. Furthermore, plasma-enhanced atomic layer deposition (PEALD) can be used to deposit a uniform thin film with high density and low defects at low temperatures, to reduce the impact of interfacial reactions on electrical properties at high temperatures. In this study, TiO₂ was deposited using PEALD, using substrates of Pt and Ru treated with rapid thermal annealing at 500 and 600 ℃, to compare structural, chemical, and electrical characteristics with reference to a TiN substrate. As a result, leakage current was suppressed to around 10^-6 A/cm² at 1 V, and an EOT at the 0.5 nm level was achieved.

• 한국진공학회지
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• 제19권1호
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• pp.10-13
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• 2010

본 논문은 N-face n-type GaN 표면에 산소 플라즈마 처리에 의해서 오믹전극과 접촉 저항을 낮추기 위한 연구를 하였다. 120초 산소 플라즈마 처리후 Ti (50 nm) / Al (35 nm)을 증착한 결과 오믹 전극을 구현하였으며, $1.25{\times}10^{-3}\;{\Omega}cm^2$의 접촉저항을 보였다. 이는 산소 플라즈마 처리가 기존의 플라즈마 처리와 같이 질소결원이 발생하였기 때문이다. 이를 통해 쇼트키장벽 높이(SBH)이 낮아지게 되었고, 오믹 전극및 플라즈마 처리를 안 한 경우보다 더 낮은 접촉저항의 결과를 획득하였다.