a-Si:H Photodiode Using Alumina Thin Film Barrier

Hur Chang-Wu,Dimitrijev Sima The Korea Institute of Information and Commucation 2005 Journal of information and communication convergen Vol.3 No.4

A photodiode capable of obtaining a sufficient photo/ dark current ratio at both forward bias state and reverse bias state is proposed. The photodiode includes a glass substrate, an aluminum film formed as a lower electrode over the glass substrate, an alumina film formed as an insulator barrier over the aluminum film, a hydrogenated amorphous silicon film formed as a photo conduction layer over a portion of the alumina film, and a transparent conduction film formed as an upper electrode over the hydro-generated amorphous silicon film. A good quality alumina $(Al_2O_3)$ film is formed by oxidation of aluminum film using electrolyte solution of succinic acid. Alumina is used as a potential barrier between amorphous silicon and aluminum. It controls dark-current restriction. In case of photodiodes made by changing the formation condition of alumina, we can obtain a stable dark current $(\~10^{-12}A)$ in alumina thickness below $1000{\AA}$. At the reverse bias state of the negative voltage in ITO (Indium Tin Oxide), the photo current has substantially constant value of $5{\times}10^{-9}$ A at light scan of 100 1x. On the other hand, the photo/dark current ratios become higher at smaller thicknesses of the alumina film. Therefore, the alumina film is used as a thin insulator barrier, which is distinct from the conventional concept of forming the insulator barrier layer near the transparent conduction film. Also, the structure with the insulator thin barrier layer formed near the lower electrode, opposed to the ITO film, solves the interface problem of the ITO film because it provides an improved photo current/dark current ratio.

고감도 탈기체분석법을 이용한 비정질 실리콘의 수소 방출특성 연구

권오민,조재령,김가현 한국물리학회 2020 새물리 Vol.70 No.9

We address hydrogen exodiffusion of hydrogenated amorphous silicon thin films by using thermal desorption spectroscopy. Amorphous silicon has a disordered atomic structure and consists of dangling bonds, which work as electronically active defects. These defects can be passivated by hydrogen, and the material is called hydrogenated amorphous silicon. Hydrogen exodiffusion provides information on Si-H bonding and the microstructure of the material. In this work, we fabricated a series of hydrogenated amorphous silicon thin films of different thicknesses and analyzed the Si-H bonding and the microstructure of the films by using hydrogen exodiffusion. In particular, we observed that the 10-nm thin film showed porous microstructure because the film was still in island/channeling stage of film deposition at initial moments, which is premature for uniform film growth. A complementary analysis using Fourier-transform infrared spectroscopy gave consistent results. 본 연구에서는 고감도 탈기체분석장비를 이용한 비정질 실리콘의 수소 방출 특성 관찰결과를 다룬다. 비정질 실리콘의 원자구조는 무질서하게 배열되어 있으며 전기적 결함으로 작용하는 댕글링 본드를함유하고 있는데, 댕글링 본드에 수소를 결합하여 전기적 결함을 부동태화하며, 이와 같은 상태의 물질을수소화된 비정질 실리콘이라 한다. 탈기체분석법을 이용하여 수소화된 비정질 실리콘의 수소 방출특성을 관찰하면 수소화된 비정질 실리콘 내 Si-H결합과 박막의 미세구조에 대한 정보를 얻을 수 있다. 본 연구에서는 동일 공정조건으로 두께를 다르게 하여 증착한 수소화된 비정질 실리콘 박막의 수소 방출특성을 관찰하였으며, 박막 두께에 따른 박막의 미세구조의 변화를 관찰하였다. 박막이 10 nm 정도로얇을 경우에는 화학기상증착의 원리에 따라 박막 성장 초기에 아일랜드 상의 미세구조를 취할 것으로유추하였으며 푸리에변환 타원편광분광분석법을 이용한 상보적 분석을 통해 일관성있는 관찰결과를 얻게되었다.

Fabrication of a Hydrogenated a-Si Photodiode

Hur, Chang-Wu The Korea Institute of Information and Commucation 2003 Journal of information and communication convergen Vol.1 No.1

A photodiode capable of obtaining a sufficient photo/dark current ratio at both a forward bias state and a reverse bias state is proposed. The photodiode includes a glass substrate, an aluminum film formed as a lower electrode over the glass substrate, an alumina film formed as a schottky barrier over the aluminum film, a hydrogenated amorphous silicon film formed as a photo conduction layer over a portion of the alumina film, and a transparent conduction film formed as an upper electrode over the hydro-generated amorphous silicon film. Growth of high quality alumina($Al_{2}O_{3}$) film using anodizing technology is proposed and analyzed by experiment. We have obtained the film with a superior characteristics

P/i interfacial engineering in semi-transparent silicon thin film solar cells for fabrication at a low temperature of 150 °C

Choi, Soo-Won,Yang, Johwa,Park, Jae-Ho,Han, Se-Jin,Song, Pungkeun,Kang, Dong-Won,Kwon, Jung-Dae Elsevier 2019 Current Applied Physics Vol.19 No.10

<P><B>Abstract</B></P> <P>In this study, we aimed to develop semitransparent solar cells (STSCs) using hydrogenated amorphous silicon (a-Si:H) at a low temperature of 150 °C to support the fabrication of flexible solar modules, applicable in building-integrated photovoltaics (BIPV). To compensate for the presumable loss of device performance at such a low processing temperature, careful control of the p/i interface is proposed. We fabricated buffer layers with hydrogen (H<SUB>2</SUB>)/silane (SiH<SUB>4</SUB>) gas flow ratios (R) ranging from 4 to 16 (R<SUB>4</SUB>–R<SUB>16</SUB>) to investigate their characteristics and incorporate them at the p/i interface by considering energy band matching. By employing this buffer, the power conversion efficiency (PCE) of a STSC was improved from 4.83% to 5.57% which is the best record in a-Si:H STSCs processed at a low temperature of 150 °C. This p/i interfacial buffer can support the realization of flexible a-Si:H-based BIPV systems using plastic- or polymer-based substrates.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Semitransparent solar cells (STSCs) were made using hydrogenated amorphous silicon. </LI> <LI> All materials were prepared at low temperature less than 150 °C. </LI> <LI> Stratified intrinsic absorbers were applied for energy band matching at p/i interface. </LI> <LI> The power conversion efficiency of STSC improved from 4.83% to 5.57%. </LI> </UL> </P>

Study of Hydrogenated Silicon Thin Film Deposited by Using Dual-frequency Inductively-coupled Plasma-enhanced Chemical-vapor Deposition

정호범,김경남,이내응,염근영 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.63 No.6

Microcrystalline silicon thin films were deposited using an inductively-coupled plasma sourcewith an internal linear-type antenna in the dual frequency mode (2 MHz/13.56 MHz), and thecharacteristics of the thin film and the plasma were investigated as functions of the relative powerratio. The deposition was performed in the SiH4 depletion condition at a deposition rate of about10 °A/s to improve the microstructural properties of the film. In the dual-frequency mode, thecrystalline volume fraction could be increased by increasing the low-frequency power, which isadded to the fixed 13.56 MHz rf power without changing the microstructure factor (R), which isrelated to defects in the crystal structure. The differences appear to be related to the lower-energyion bombardment of the substrate in the dual-frequency mode. In addition, by increasing the lowfrequencypower from 0 to 1.5 kW while keeping 3 kW at 13.56 MHz, we were able to change theuniformity of the deposition from 15.5% to less than 10% an improvement.

고효율 실리콘 박막태양전지를 위한 신규 수소저감형 비정질실리콘 산화막 버퍼층 개발

강동원(Dong-Won Kang) 대한전기학회 2016 전기학회논문지 Vol.65 No.10

We propose a novel hydrogen-reduced p-type amorphous silicon oxide buffer layer between TiO₂ antireflection layer and p-type silicon window layer of silicon thin film solar cells. This new buffer layer can protect underlying the TiO₂ by suppressing hydrogen plasma, which could be made by excluding H2 gas introduction during plasma deposition. Amorphous silicon oxide thin film solar cells with employing the new buffer layer exhibited better conversion efficiency (8.10 %) compared with the standard cell (7.88 %) without the buffer layer. This new buffer layer can be processed in the same p-chamber with in-situ mode before depositing main p-type amorphous silicon oxide window layer. Comparing with state-of-the-art buffer layer of AZO/p-nc-SiOx:H, our new buffer layer can be processed with cost-effective, much simple process based on similar device performances.

Flash-lamp-crystallized polycrystalline silicon films with remarkably long minority carrier lifetimes

Keisuke Ohdaira,Hiroyuki Takemoto,Takuya Nishikawa,Hideki Matsumura 한국물리학회 2010 Current Applied Physics Vol.10 No.3

Polycrystalline silicon (poly-Si) films formed by flash lamp annealing (FLA) of precursor a-Si films are found to hardly lose hydrogen (H) atoms during crystallization and keep the initial H concentration on the order of 1021/㎤. Short annealing duration and sufficient Si film thickness would lead to the suppression of H desorption. A characteristic lateral crystallization mechanism, referred to as explosive crystallization (EC), may also contribute to the prevention of H desorption due to rapid lateral heat diffusion into neighboring a-Si. Poly-Si films after annealing under N2 or forming gas ambient shows remarkably long minority carrier lifetime compared to untreated films, indicating effective defect termination by H atoms remaining in the poly-Si films.

Boron-doped hydrogenated mixed-phase silicon as thermo-sensing films for infrared detectors

Phong Pham, Duy,Park, Jinjoo,Shin, Chonghoon,Kim, Sangho,Nam, Yonghyun,Kim, Geunho,Kim, Minsik,Yi, Junsin Elsevier 2018 Materials science in semiconductor processing Vol.74 No.-

<P><B>Abstract</B></P> <P>Silicon materials have been widely used as thermo-sensing layers in infrared detectors or uncooled micro-bolometers. Parameters such as a large thermal coefficient of resistance (TCR), low sheet resistance (R<SUB>s</SUB>), and low 1/f noise are important for high performance of these devices. However, there is always a trade-off between these parameters. For example, the crystalline silicon materials typically exhibit low R<SUB>s</SUB> and 1/f noise, and significantly low TCR, while the amorphous silicon materials generally have large TCR, and considerably high R<SUB>s</SUB> and 1/f noise. Consequently, the best trade-off can be achieved by using a mixed-phase structure of silicon materials, i.e. an intermediate form between the crystalline and amorphous structures. Herein we report the important characteristics of hydrogenated mixed-phase silicon films, deposited by the plasma-enhanced chemical vapour deposition process, for infrared detectors. The films in the mixed-phase structure showed high TCR values in the range of 2–3%K<SUP>–1</SUP> and moderate sheet resistances in range of 10–40MΩsq<SUP>−1</SUP>. These results indicate that the mixed-phase silicon films are potential alternatives to conventional boron doped hydrogenated amorphous and microcrystalline silicon films for use as thermo-sensing layers in infrared detectors.</P>

Investigations on Microcrystalline Silicon Films for Solar Cell Application

Hwang, Hae-Sook,Park, Min-Gyu,Ruh, Hyun,Yu, Hyun-Ung Korean Chemical Society 2010 Bulletin of the Korean Chemical Society Vol.31 No.10

Hydrogenated microcrystalline silicon (${\mu}c$-Si:H) thin film for solar cells is prepared by plasma-enhanced chemical vapor deposition and physical properties of the ${\mu}c$-Si:H p-layer has been investigated. With respect to stable efficiency, this film is expected to surpass the performance of conventional amorphous silicon based solar cells and very soon be a close competitor to other thin film photovoltaic materials. Silicon in various structural forms has a direct effect on the efficiency of solar cell devices with different electron mobility and photon conversion. A Raman microscope is adopted to study the degree of crystallinity of Si film by analyzing the integrated intensity peaks at 480, 510 and $520\;cm^{-1}$, which corresponds to the amorphous phase (a-Si:H), microcrystalline (${\mu}c$-Si:H) and large crystals (c-Si), respectively. The crystal volume fraction is calculated from the ratio of the crystalline and the amorphous phase. The results are compared with high-resolution transmission electron microscopy (HR-TEM) for the determination of crystallinity factor. Optical properties such as refractive index, extinction coefficient, and band gap are studied with reflectance spectra.

Investigations on Microcrystalline Silicon Films for Solar Cell Application

황혜숙,Min Gyu Park,Hyun Ruh,Hyunung Yu 대한화학회 2010 Bulletin of the Korean Chemical Society Vol.31 No.10

Hydrogenated microcrystalline silicon (μc-Si:H) thin film for solar cells is prepared by plasma-enhanced chemical vapor deposition and physical properties of the μc-Si:H p-layer has been investigated. With respect to stable efficiency,this film is expected to surpass the performance of conventional amorphous silicon based solar cells and very soon be a close competitor to other thin film photovoltaic materials. Silicon in various structural forms has a direct effect on the efficiency of solar cell devices with different electron mobility and photon conversion. A Raman microscope is adopted to study the degree of crystallinity of Si film by analyzing the integrated intensity peaks at 480, 510 and 520 cm‒1, which corresponds to the amorphous phase (a-Si:H), microcrystalline (μc-Si:H) and large crystals (c-Si),respectively. The crystal volume fraction is calculated from the ratio of the crystalline and the amorphous phase. The results are compared with high-resolution transmission electron microscopy (HR-TEM) for the determination of crystallinity factor. Optical properties such as refractive index, extinction coefficient, and band gap are studied with reflectance spectra.