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  • Title/Summary/Keyword: 이종재료 접합

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Fabrication and characterization of the SiGe HBTs using an RPCVD (RPCVD를 이용한 실리콘 게르마늄 이종 접합 바이폴라 트랜지스터 제작 및 특성 분석)

  • 한태현;서광열
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.17 no.8
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    • pp.823-829
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    • 2004
  • In this paper, non-self-aligned SiGe HBTs with fτ andfmaxabove 50 GHz have been fabricated using an RPCVD(Reduced Pressure Chemical Vapor Deposition) system for wireless applications. In the proposed structure, in-situ boron doped selective epitaxial growth(BDSEG) and TiSi2 were used for the base electrode to reduce base resistance and in-situ phosphorus doped polysilicon was used for the emitter electrode to reduce emitter resistance. SiGe base profiles and collector design methodology to increase fτ andfmax are discussed in detail. Two SiGe HBTs with the collector-emitter breakdown voltages BVCEO of 3 V and 6 V were fabricated using SIC(selective ion-implanted collector) implantation. Fabricated SiGe HBTs have a current gain of 265 ∼ 285 and Early voltage of 102 ∼ 120 V, respectively. For the 1×8μm2 emitter, a SiGe HBT with BVCEO= 6 V shows a cut-off frequency, fτof 24.3 GHz and a maximum oscillation frequency, fmaxof 47.6 GHz at Icof 3.7 mA andVCE of 4 V. A SiGe HBT with BVCEO = 3 V shows fτof 50.8 GHz and fmax of 52.2 GHz at Ic of 14.7 mA and VCE of 2 V.

Effect of Work Function of Zn-doped ITO Thin Films on Characteristics of Silicon Heterojunction Solar Cells (실리콘 이종접합 태양전지 특성에 대한 Zn 도핑된 ITO 박막의 일함수 효과)

  • Lee, Seung-Hun;Tark, Sung-Ju;Choi, Su-Young;Kim, Chan-Seok;Kim, Won-Mok;Kim, Dong-Hhwan
    • Korean Journal of Materials Research
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    • v.21 no.9
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    • pp.491-496
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    • 2011
  • Transparent conducting oxides (TCOs) used in the antireflection layer and current spreading layer of heterojunction solar cells should have excellent optical and electrical properties. Furthermore, TCOs need a high work function over 5.2 eV to prevent the effect of emitter band-bending caused by the difference in work function between emitter and TCOs. Sn-doped In2O3 (ITO) film is a highly promising material as a TCO due to its excellent optical and electrical properties. However, ITO films have a low work function of about 4.8 eV. This low work function of ITO films leads to deterioration of the conversion efficiency of solar cells. In this work, ITO films with various Zn contents of 0, 6.9, 12.7, 28.8, and 36.6 at.% were fabricated by a co-sputtering method using ITO and AZO targets at room temperature. The optical and electrical properties of Zn-doped ITO thin films were analyzed. Then, silicon heterojunction solar cells with these films were fabricated. The 12.7 at% Zn-doped ITO films show the highest hall mobility of 35.71 cm2/Vsec. With increasing Zn content over 12.7, the hall mobility decreases. Although a small addition of Zn content increased the work function, further addition of Zn content over 12.7 at.% led to decreasing electrical properties because of the decrease in the carrier concentration and hall mobility. Silicon heterojunction solar cells with 12.7 at% Zn-doped ITO thin films showed the highest conversion efficiency of 15.8%.

Fabrication and Characterization of CuO Thin Film/ZnO Nanorods Heterojunction Structure for Efficient Detection of NO Gas (일산화질소 가스 검출을 위한 CuO 박막/ZnO 나노막대 이종접합 구조의 제작 및 특성 평가)

  • Yoo, Hwansu;Kim, Hyojin;Kim, Dojin
    • Korean Journal of Materials Research
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    • v.28 no.1
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    • pp.32-37
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    • 2018
  • We report on the efficient detection of NO gas by an all-oxide semiconductor p-n heterojunction diode structure comprised of n-type zinc oxide (ZnO) nanorods embedded in p-type copper oxide (CuO) thin film. The CuO thin film/ZnO nanorod heterostructure was fabricated by directly sputtering CuO thin film onto a vertically aligned ZnO nanorod array synthesized via a hydrothemal method. The transport behavior and NO gas sensing properties of the fabricated CuO thin film/ZnO nanorod heterostructure were charcterized and revealed that the oxide semiconductor heterojunction exhibited a definite rectifying diode-like behavior at various temperatures ranging from room temperature to 250C. The NO gas sensing experiment indicated that the CuO thin film/ZnO nanorod heterostructure had a good sensing performance for the efficient detection of NO gas in the range of 2-14 ppm under the conditions of an applied bias of 2 V and a comparatively low operating temperature of 150C. The NO gas sensing process in the CuO/ZnO p-n heterostructure is discussed in terms of the electronic band structure.

Selective Epitaxial Growth of Si and SiGe using Si-Ge-H-CI System for Self-Aligned HBT Applications (Si-Ge-H-CI 계를 이용한 자기정렬 HBT용 Si 및 SiGe 의 선택적 에피성장)

  • Kim, Sang-Hoon;Shim, Kyu-Hwan;Kang, Jin-Young
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2002.11a
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    • pp.182-185
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    • 2002
  • 자기정렬구조의 실리콘-게르마늄 이종접합 트랜지스터에서 fmax를 높이기 위한 방안으로 베이스의 저항 값을 감소시키고자 외부 베이스에 실리콘 및 실리콘-게르마늄 박막을 저온에서 선택적으로 성장할 수 있는 방법을 연구하였다. RPCVD를 이용하여 SiH2Cl2GeH4를 소스 가스로 하고 HCI을 첨가하여 선택성을 향상시킴으로써 675725C의 저온에서도 실리콘 및 실리콘-게르마늄의 선택적 에피성장이 가능하였다. 고온 공정에 주로 이용되는 SiH2Cl2를 이용한 실리콘 증착은 675C에서 열분해가 잘 이루어지지 않고 HCl의 첨가에 의한 식각반응이 동시에 진행되어 실리콘 기판에서도 증착이 진행되지 않으나 700C 이상에서는 HCI을 첨가한 경우에 한해서 선택성이 유지되면서 실리콘의 성장이 이루어졌다, 반면 실리콘-게르마늄막은 실리콘에 비해 열분해 온도가 낮고 GeO를 형성하여 잠입시간을 지연하는 효과가 있는 게르마늄의 특성으로 인해 선택성이나 증착속도 모두에서 유리하였으나 실리사이드 공정시에 표면으로 게르마늄이 석출되는 현상 등의 저항성분이 크게 작용하여 실리콘-게르마늄막 만으로는 외부 베이스에의 적용은 적절하지 않았다. 그러나 실리콘막을 실리콘-게르마늄막 위에 Cap 층으로 증착하거나 실리콘막 만으로 외부 베이스에 선택적으로 증착하여 베이스의 저항을 70% 가량 감소시킬 수 있었다.

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Properties of the RF Sputter Deposited n-ZnO Thin-Film and the n-ZnO/p-GaN heterojunction LED (RF스퍼터링법으로 성장시킨 n-ZnO 박막과 n-ZnO/p-GaN 이종접합 LED의 특성)

  • Shin, Dongwhee;Byun, Changsub;Kim, Seontai
    • Korean Journal of Materials Research
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    • v.23 no.3
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    • pp.161-167
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    • 2013
  • The ZnO thin films were grown on GaN template substrates by RF magnetron sputtering at different RF powers and n-ZnO/p-GaN heterojunction LEDs were fabricated to investigate the effect of the RF power on the characteristics of the n-ZnO/p-GaN LEDs. For the growth of the ZnO thin films, the substrate temperature was kept constant at 200C and the RF power was varied within the range of 200 to 500W at different growth times to deposit films of 100 nm thick. The electrical, optical and structural properties of ZnO thin films were investigated by ellipsometry, X-ray diffraction (XRD), atomic force microscopy (AFM), photoluminescence (PL) and by assessing the Hall effect. The characteristics of the n-ZnO/p-GaN LEDs were evaluated by current-voltage (I-V) and electroluminescence (EL) measurements. ZnO thin films were grown with a preferred c-axis orientation along the (0002) plane. The XRD peaks shifted to low angles and the surface roughness became non-uniform with an increase in the RF power. Also, the PL emission peak was red-shifted. The carrier density and the mobility decreased with the RF power. For the n-ZnO/p-GaN LED, the forward current at 20 V decreased and the threshold voltage increased with the RF power. The EL emission peak was observed at approximately 435 nm and the luminescence intensity decreased. Consequently, the crystallinity of the ZnO thin films grown with RF sputtering powers were improved. However, excess Zn affected the structural, electrical and optical properties of the ZnO thin films when the optimal RF power was exceeded. This excess RF power will degrade the characteristics of light emitting devices.

Trapezoidal Gate 구조를 이용한 AlGaN/GaN HEMT의 DC 및 고내압 특성 연구

  • Kim, Jae-Mu;Kim, Dong-Ho;Kim, Su-Jin;Jeong, Gang-Min
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2008.06a
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    • pp.151-151
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    • 2008
  • 갈륨-질화물(GaN) 기반의 고속전자이동도 트랜지스터(high electron mobility transistor, HEMT)는 마이크로파 또는 밀리미터파 등과 같은 고주파 대역의 통신시스템에 널리 사용되는 전자소자로 각광받고 있다. GaN HEMT는 AlGaN/GaN 또는 AlGaN/InGaN/GaN 등과 같은 이종접합구조(heterostructure)로부터 발생하는 이차원 전자가스(two-dimensional electron gas, 2DEG) 채널을 이용하여 캐리어 구속효과(carrier confinement) 및 이동도의 향상이 가능하다. 또한 높은 2DEG 채널의 면밀도(sheet concentration) 와 전자의 포화 속도(saturation velocity)를 바탕으로 고출력 동작이 가능하여 차세대 이동통신용 전력 증폭기로 주목받고 있다. 그러나 이론적으로 우수한 특성과 달리, 실제 소자에서는 epi 성장시의 결함이나 전위, 표면 상태에 따른 2DEG 감소 등의 영향으로 이론보다 높은 누설 전류와 낮은 항복 전압 특성을 가진다. 특히, 기존의 GaN HEMT 구조에서는 Drain-Side Gate Edge에서의 전계 집중이 항복 전압 특성에 미치는 영향이 크다. 본 논문에서는 이러한 문제를 해결하기 위해 Trapezoidal Gate구조를 이용하여 Drain 방향의 Gate Edge가 완만히 변하는 구조를 제안하였다. 이를 위해 ATLASTM 전산모사 프로그램을 이용하여 Trapezoidal Gate 구조를 구현하여 형태에 따른 전류-전압 특성 및 소자의 스위칭 특성 및 Gate 아래 채널층에 형성되는 Electric Field의 분산을 조사하고, 이를 바탕으로 고속 동작 및 높은 항복 전압을 갖는 AlGaN/GaN HEMT의 최적화된 구조를 제안하였다. 새로운 구조의 Gate를 적용한 AlGaN/GaN HEMT는 Gate edge에서의 전계를 분산시켜 피크 값이 감소되는 것을 확인하였다.

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Influence of Mg composition on growth and characteristic of MgZnO/ZnO heterostructure (MgZnO/ZnO 이종접합구조의 특성과 성장에 Mg 합성이 미치는 영향)

  • Kim, Young-Yi;Kong, Bo-Hyun;Kim, Dong-Chan;An, Cheol-Hyeon;Han, Won-Seok;Choe, Mi-Gyeong;Jo, Hyeong-Gyun;Moon, Jin-Young;Lee, Ho-Seung
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2008.06a
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    • pp.73-73
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    • 2008
  • 일반적으로 청색 및 자외선 발광다이오드, 레이저 다이오드, UV 감지기 (detector)소자 등의 기술적인 중요성은 ZnO를 기반으로 하는 산화물 반도체와 함께 와이드 밴드갭 반도체 연구가 활발히 진행되고 있다. ZnO의 경우 밴드갭 엔지니어링을 위해 일반적으로 Cd과 Mg을 사용하고 있으며 특히, ZnO에 Mg을 첨가하여 MgZnO 화합물을 첨가할 경우 밴드갭을 3.3eV~7.8eV까지 증가 시킬 수 있고, MgZnO/ZnO 초격자 구조를 이용할 경우 자유 엑시톤 결합에너지를 100meV 이상까지 증가시킬 수 있는 장점을 가지고 있다. 그러나 MgO는 결정구조가 rocksalt 구조를 가지는 입방정 구조이기 때문에 Hexagonal 구조를 가진 ZnO에 첨가될 경우 고용도에 큰 제한을 가지게 된다. 이와 같은 문제점으로 인하여 밴드갭 엔지니어링 기술은 여전히 해결되지 않은 문제점으로 남아 있다. 본 실험에서는 RF 마그네트론 스퍼터링 방법으로 사파이어 기판위에 MgZnO/ZnO 박막을 co-sputtering 시켰다. Targer은 ZnO(99.999%) 와 MgO (99.999%) target을 사용하였고, 스퍼터링 가스는 아르곤과 산소가스를 2:1 비율로 혼합시켜 성장하였다. MgZnO 박막을 성장하기 전 ZnO 층을 ~500 두께로 성장 시켰다. RF-power는 ZnO target을 고정 시키고, MgO targe power를 변화시켜 Mg 농도를 조절 하였다. 실험 결과 MgO target power 가 증가 할수록 반치폭이 증가하고, c-plane을 따라 격자 상수가 감소하는 것을 확인 할 수 있고, UV emission peak intensity가 감소며 단파장쪽으로 blue shift 하고, activation energy 가 증가하는 것을 관찰 할 수 있었다.

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Changes in Interface Properties of TCO/a-Si:H Layer by Zn Buffer Layer in Silicon Heterojunction Solar Cells (실리콘 이종접합 태양전지의 Zn 확산방지층에 의한 TCO/a-Si:H 층간의 계면특성 변화)

  • Tark, Sung-Ju;Son, Chang-Sik;Kim, Dong-Hwan
    • Korean Journal of Materials Research
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    • v.21 no.6
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    • pp.341-346
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    • 2011
  • In this study, we inserted a Zn buffer layer into a AZO/p-type a-si:H layer interface in order to lower the contact resistance of the interface. For the Zn layer, the deposition was conducted at 5 nm, 7 nm and 10 nm using the rf-magnetron sputtering method. The results were compared to that of the AZO film to discuss the possibility of the Zn layer being used as a transparent conductive oxide thin film for application in the silicon heterojunction solar cell. We used the rf-magnetron sputtering method to fabricate Al 2 wt.% of Al-doped ZnO (AZO) film as a transparent conductive oxide (TCO). We analyzed the electro-optical properties of the ZnO as well as the interface properties of the AZO/p-type a-Si:H layer. After inserting a buffer layer into the AZO/p-type a-Si:H layers to enhance the interface properties, we measured the contact resistance of the layers using a CTLM (circular transmission line model) pattern, the depth profile of the layers using AES (auger electron spectroscopy), and the changes in the properties of the AZO thin film through heat treatment. We investigated the effects of the interface properties of the AZO/p-type a-Si:H layer on the characteristics of silicon heterojunction solar cells and the way to improve the interface properties. When depositing AZO thin film on a-Si layer, oxygen atoms are diffused from the AZO thin film towards the a-Si layer. Thus, the characteristics of the solar cells deteriorate due to the created oxide film. While a diffusion of Zn occurs toward the a-Si in the case of AZO used as TCO, the diffusion of In occurs toward a-Si in the case of ITO used as TCO.

MoO3/p-Si Heterojunction for Infrared Photodetector (MoO3 기반 실리콘 이종접합 IR 영역 광검출기 개발)

  • Park, Wang-Hee;Kim, Joondong;Choi, In-Hyuk
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.30 no.8
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    • pp.525-529
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    • 2017
  • Molybdenum oxide (MoO3) offers pivotal advantages for high optical transparency and low light reflection. Considering device fabrication, n-type MoO3 semiconductor can spontaneously establish a junction with p-type Si. Since the energy bandgap of Si is 1.12 eV, a maximum photon wavelength of around 1,100 nm is required to initiate effective photoelectric reaction. However, the utilization of infrared photons is very limited for Si photonics. Hence, to enhance the Si photoelectric devices, we applied the wide energy bandgap MoO3 (3.7 eV) top-layer onto Si. Using a large-scale production method, a wafer-scale MoO3 device was fabricated with a highly crystalline structure. The MoO3/pSi heterojunction device provides distinct photoresponses for long wavelength photons at 900 nm and 1,100 nm with extremely fast response times: rise time of 65.69 ms and fall time of 71.82 ms. We demonstrate the high-performing MoO3/pSi infrared photodetector and provide a design scheme for the extension of Si for the utilization of long-wavelength light.

The Effects of Lithium-Incorporated on N-ZTO/P-SiC Heterojunction Diodes by Using a Solution Process (용액공정으로 제작한 리튬 도핑된 N-ZTO/P-SiC 이종접합 구조의 전기적 특성)

  • Lee, Hyun-Soo;Park, Sung-Joon;An, Jae-In;Cho, Seulki;Koo, Sang-Mo
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.31 no.4
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    • pp.203-207
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    • 2018
  • In this work, we investigate the effects of lithium doping on the electric performance of solution-processed n-type zinc tin oxide (ZTO)/p-type silicon carbide (SiC) heterojunction diode structures. The proper amount of lithium doping not only affects the carrier concentration and interface quality but also influences the temperature sensitivity of the series resistance and activation energy. We confirmed that the device characteristics vary with lithium doping at concentrations of 0, 10, and 20 wt%. In particular, the highest rectification ratio of 1.89×107 and the lowest trap density of 4.829×1,022cm2 were observed at 20 wt% of lithium doping. Devices at this doping level showed the best characteristics. As the temperature was increased, the series resistance value decreased. Additionally, the activation energy was observed to change with respect to the component acting on the trap. We have demonstrated that lithium doping is an effective way to obtain a higher performance ZTO-based diode.