• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.61.1-61.1
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• 2011

We report on a detailed study on gap-state distribution in thin amorphous silicon layers(a-Si:H) with film thickness between 5 nm and 20 nm c-Si wafers performed by UV excited photoelectron spectroscopy(UV-PES). We measured how the work function, the gap state density, the position of the Fermi-level and the Urbch-energy depend on the layer thickness and the doping level of the ultra thin a-Si:H(n) layer. It was found, that for phosphorous doping the position of the Fermi level saturates at $E_F-E_V$=1.47 eV. This is achieved at a gas phase concentration of 10000 ppm $PH_3$ in the $SiH_4/H_2$ mixture which was used for the PECVD deposition process. The variation of the doping level from 0 to 20000 ppm $PH_3$ addition results in an increase of the Urbach energy from 65 meV to 101 meV and in an increase of the gap state density at midgap($E_i-E_V$=0.86eV) from $3{\times}10^{18}$ to $2{\times}1019cm^{-3}eV^{-1}$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.5
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• pp.320-323
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• 2018

SiGe thin films were deposited by remote plasma enhanced chemical vapor deposition (RPE-CVD) at $400^{\circ}C$ using $SiH_4$ or $SiCl_4$ and $GeCl_4$ as the source of Si and Ge, respectively. The growth rate and the degree of crystallinity of the fabricated films were characterized by scanning electron microscopy and Raman analysis, respectively. The optical and electrical properties of SiGe films fabricated using $SiCl_4$ and $SiH_4$ source were comparatively studied. SiGe films deposited using $SiCl_4$ source showed a lower growth rate and higher crystallinity than those deposited using $SiH_4$ source. Ultraviolet and visible spectroscopy measurement showed that the optical band gap of SiGe is in the range of 0.88~1.22 eV.

• Journal of the Korean Ceramic Society
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• v.48 no.6
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• pp.621-624
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• 2011

In order to deposit a homogeneous and uniform ${\beta}$-SiC films by chemical vapor deposition, we constructed the phase-diagram of ${\beta}$-SiC over graphite and silicon via computational thermodynamic calculation considering pressure(P), temperature(T) and gas composition(C) as variables in $C_3H_8-SiCl_4-H_2$ system. During the calculation, the ratio of Cl/Si and C/Si is maintained to be 4 and 1, respectively, and H/Si ratio is varied from 2.67 to 15,000. The P-T-C diagram showed very steep phase boundary between SiC+C and SiC region perpendicular to H/Si axis and also showed SiC+Si region with very large H/Si value of ~6700. The diagram can be applied not only to the prediction of the deposited phase composition but to compositional variation due to the temperature distribution in the reactor. The P-T-C diagram could provide the better understanding of chemical vapor deposition of silicon carbide.

• Korean Journal of Crystallography
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• v.3 no.2
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• pp.98-110
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• 1992

B-SiC thin films were fabricated on Si(100) substrate under 1 atom by fVD. The effects of deposition conditions on the growth and the properties especially crystallinity and prefer ential alignment of these thin films were investigated. SiH4 and CH4 were used as source gases and H2 as Carrier gas. Th9 growth Of B-SiC thin films with changing parameters such as the growth temperature, the ratio of source gases (SiH4/CH4 ) and the total amount of source gases. The grown thin films were characterized by using SEM, a -step, XRD, Raman Spectro- scopy and TEM. Chemical conversion process improved the quality of thin films due to the formation of SiC buffer layer. The crystallinity of SiC thin films was improved when the growth temperature was higher than l150t and the amount of CH4 exceeded that of SiH4. The better crystallinity, the better alignment to the crystalline direction of substates. TEM analyses of the good quality thin films showed that the grain size was bigger at the surface than at the interface and the defect density is not depend on the ratio of the source gases.

• Journal of the Korean Vacuum Society
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• v.18 no.6
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• pp.426-434
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• 2009

A global simulation of $SiH_4/H_2$ discharge is conducted in a planar-type inductively coupled plasma (ICP) discharge. We numerically solve a set of spatially averaged fluid equations for electrons, positive ions, negative ions, neutrals, and radicals. Absorbed power by electrons is determined by an analytic electron heating theory including the anomalous skin effect. Also, we investigate functional dependence of various discharge quantities such as the densities of various species and the temperature of electron on external controllable parameters such as ratio between $SiH_4$ and $H_2$, power and pressure.

• Journal of IKEEE
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• v.18 no.4
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• pp.447-455
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• 2014

In this research, n-based 4H-MOS Capacitor was fabricated with PECVD (plasma enhanced chemical vapor deposition) process for improving SiC/$SiO_2$ interface properties known as main problem of 4H-SiC MOSFET. To overcome the problems of dry oxidation process such as lower growth rate, high interface trap density and low critical electric field of $SiO_2$, PECVD and NO annealing processes are used to MOS Capacitor fabrication. After fabrication, MOS Capacitor's interface properties were measured and evaluated by hi-lo C-V measure, I-V measure and SIMS. As a result of comparing the interface properties with the dry oxidation case, improved interface and oxide properties such as 20% reduced flatband voltage shift, 25% reduced effective oxide charge density, increased oxide breakdown field of 8MV/cm and best effective barrier height of 1.57eV, 69.05% reduced interface trap density in the range of 0.375~0.495eV under the conduction band are observed.

• 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.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.128.2-128.2
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• 2011

스테인레스 스틸 유연기판 위에 플라즈마 화학기상 증착법 (plasma enhanced chemical vapor deposition)을 이용하여 nip 구조의 미세결정질 실리콘 박막 태양전지 (microcrystalline silicon thin film solar cell)를 제조하고 i ${\mu}c$-Si:H광 흡수층과 p ${\mu}c$-Si:H 사이에 i a-Si:H 버퍼 층을 삽입하여 i/p 계면특성을 개선하고 이에 따른 태양전지 성능특성 변화를 조사하였다. ${\mu}c$-Si:H 박막으로 이루어진 i/p 계면에서의 구조적, 전기적 결함은 태양전지 내에서 생성된 캐리어의 재결합과 shunt resistance 감소를 초래하여 개방전압 (open circuit voltage) 및 곡선 인자 (fill factor)를 감소시키는 것으로 알려졌다. 제조된 미세결정질 실리콘 박막 태양전지는 SUS/Ag/ZnO:Al/n ${\mu}c$-Si:H/i ${\mu}c$-Si:H/p ${\mu}c$-Si:H 구조로 제작되었으며 i/p 계면 사이의 i a-Si;H 버퍼층 두께를 변화시키고 이에 따른 태양전지의 특성을 조사하였다. 태양전지의 구조적, 전기적 특성 변화는 Scanning Electron Microscope (SEM), UV-visible-nIR spectrometry, Photo IV와 Dark IV를 통하여 조사하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.521-524
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• 2001

In this letter. we report on the investigation of Ti. Pt/Si/Ti Ohmic contacts to p-type 4H-SiC. The contacts were formed by a 2-step vacuum annealing at $500^{\circ}C$ for 1h. $950^{\circ}C$ for 10 min respectively. The contact resistances were measured using the transmission line model method. which resulted in specific contact resistivities in the $3.5{\times}10^{-3}$ and $6.2{\times}10^{-4}ohm/cm^{2}$, and the physical properties of the contacts were examined using x-ray diffraction. microscopy. AES(auger electron spectroscopy). AES analysis has shown that, at this anneal temperature, there was a intermixing of the Ti and Si. migration of into SiC. Overlayer of Pt had the effect of decreasing the specific contact resistivity and improving the surface morphology of the annealed contact.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.88-88
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• 2009

실리콘 이종접합 태양전지 제작을 위한 주요 요소기술 중 TCO/a-Si:H 간의 계면 특성은 태양전지 효율을 결정하는 주요 인자이다. 일반적으로 투명전도 산화막으로는 ZnO:Al 또는 ITO 가 사용되고 있으며 Zn, In, Sn, O 등의 확산과 Si원소의 확산으로 TCO/a-Si:H 계면에서 $SiO_x$가 생성되어 태양전지 충진률을 감소시키는 영향을 미친다. 따라서 본 연구에서는 TCO/a-Si 계면에서 확산을 방지 하면서 패시베이션 역할을 하는 완충층을 삽입하여 실리콘 이종접합 태양전지의 효율을 높이는 연구를 수행하였다. 완충층으로 사용된 ZnO:Al의 수소화와 Zn 박막, $TiO_2$ 박막의 전기 광학적 특성을 분석하였고 AES 분석을 통해 $SiO_x$의 생성과 각 원소의 확산정도를 분석하고, CTLM을 이용하여 TCO/완충층/a-Si 간의 접촉저항을 측정하였다. 결과적으로 완충층으로 사용된 $TiO_2$(5nm)는 광특성에 큰 감소요인 없이 전기적 특성과 접촉저항 특성이 우수하였으며, 원소들간의 확산방지층으로도 우수한 특성을 보였다. ZnO:Al의 수소화는 SIMS 분석 결과 수소원소들이 계면쪽에 위치하지 않고 표면쪽에 다수 존재함으로써 패시베이션 특성을 크게 보이지 않았으나 AZO 박막의 전기적 특성은 크게 향상 시켰다. 그밖에 완충층으로 사용된 Zn 박막은 두께가 두꺼원 질수록 접촉저항의 감소를 가져왔으나 광학적 특성이 크게 감소하면서 효율적인 광포획 특성을 가지지 못하였다. 본 연구를 통하여 TCO/a-Si:H 간의 완충층 삽입을 통해 접촉저항을 낮추고 원소간의 확산을 억제하여 계면 패시베이션 특성을 향상 시킬수 있었다.