• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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• pp.228-231
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• 2006

This paper briefly introduces silicon based thin film solar cells: amorphous (a-Si:H), microcrystalline ${\mu}c-Si:H$ single junction and $a-Si:H/{\mu}c-Si:H$ tandem solar cells. The major difference of a-Si:H and ${\mu}c-Si:H$ cells comes from electro-optical properties of intrinsic Si-films (active layer) that absorb incident photon and generate electron-hole pairs. The a-Si:H film has energy band-gap (Eg) of 1.7-1.8eV and solar cells incorporating this wide Eg a-Si:H material as active layer commonly give high voltage and low current, when illuminated, compared to ${\mu}c-Si:H$ solar cells that employ low Eg (1.1eV) material. This Eg difference of two materials make possible tandem configuration in order to effectively use incident photon energy. The $a-Si:H/{\mu}c-Si:H$ tandem solar cells, therefore, have a great potential for low cost photovoltaic device by its various advantages such as low material cost by thin-film structure on low cost substrate instead of expensive c-Si wafer and high conversion efficiency by tandem structure. In this paper, the structure, process and operation properties of Si-based thin-film solar cells are discussed.

• Korean Journal of Materials Research
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• v.8 no.4
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• pp.359-361
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• 1998

Visible photoluminescence(PU was observed from hydrogenated amorphous silicon deposited on silicon(a-Si : H/Si) using electron cyclotron resonance plasma enhanced chemical vapor deposition (ECR- PECVD) with silane ($SiH_{4}$) gas as the reactant source. The PL spectra from a-Si : H/Si were very similar to those from porous silicon. Hydrogen contents of samples annealed under oxygen atmosphere for 2minutes at $500^{\circ}C$ by rapid thermal annealing were reduced to 1~2%, and the samples did not show visible PL, indicating that hydrogen has a very important role in the PL process of a- Si : H/Si. As the thickness of deposited a-Si : H film increased, PL intensity decreased. The visi¬ble PL from a-Si: H deposited on Si by ECR-PECVD with $SiH_{4}$ . is suggested to be from silicon hydrides formed at the interface between the Si substrate and the deposited a-Si : H film during the deposition.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.3
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• pp.468-473
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• 2003

In this paper, for enhancement of property on a-Si:H TFTs We measure interface characteristics of ferroelectrics thin film and a-Si:H thin film. First, SrTiO$_3$ thin film is deposited bye-beam evaporation. Deposited films are annealed for 1 hour in N2 ambient at $150^{\circ}C∼600^{\circ}C$. Dielectric characteristics of deposited SrTiO$_3$ films are very good because dielectric constant shows 50∼100 and breakdown electric field are 1 ∼ 1.5 MV/cm. a-SiN:H,a-Si:H(n-type a-Si:H) are deposited onto SrTiO$_3$ film to make MFNS(Meta1/ferroelectric/a-SiN:H/a-Si:H) by PECVD. After the C-V measurement for interface characteristics, MFNS structure shows no difference with MNS(Metal/a-SiN:H/a-Si:H) structure in C-V characteristics but the insulator capacitance value of MFNS structure is much higher than the MNS because of high dielectric constant of ferroelectric.

• Journal of Sensor Science and Technology
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• v.4 no.2
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• pp.58-63
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• 1995

The effects of substrate temperature, RF power, and $NH_{3}/SiH_{4}$ gas flow ratio on the dielectric constant and optical bandgap of amorphous silicon nitride (a-SiNx:H) thin films prepared by PECVD method using RF glow discharge decomposition of $SiH_{4}$ and $NH_{3}$ gas mixtures have been studied. The dielectric constant and optical bandgap of a-SiNx:H thin films were greatly exchanged as by increasing substrate temperature, RF power, and $NH_{3}/SiH_{4}$ gas flow ratio. The dielectric constant of a-SiNx:H films was increased and optical bandgap of a-SiNx:H films was decreased as the substrate temperature was increased. When the substrate temperature, RF power, gas pressure, $NH_{3}/SiH_{4}$ gas flow ratio, and thickness were $250^{\circ}C$, 20 W, 500 mTorr, 10 and $1500\;{\AA}$, respectively, the dielectric constant, breakdown field and optical bandgap of a-SiNx:H film were 4.3, 1 MV/cm, and 2.9 eV, respectively.

• Journal of Sensor Science and Technology
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• v.2 no.1
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• pp.29-34
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• 1993

a-Si : H photodiodes for image sensor have been fabricated and characterized. Photosensitivity of a ITO/a-Si : H/Al photodiode without blocking layer was 0.7 under the applied voltage of 5 V and peak spectral sensitivity in visible region was found at 620 nm. Dark current of ITO/a-SiN : H/a-Si : H/p-a-Si : H/Al photodiode was suppressed by hole blocking layer and electron blocking layer at the value of lower than 1.5 pA to the applied voltage of 10 V. Also maximum photosensitivity was about 1 under the applied voltage of 3 V and peak spectral sensitivity was found at 540 nm.

• Journal of the Korean Vacuum Society
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• v.18 no.1
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• pp.15-23
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• 2009

Saturation-coverage silyl, $-SiH_3(a)$, overlayers were prepared from $Si_2H_6$ adsorption on three comparative surfaces: clean unmodified; D-precovered; and atomically roughened Si(100). Together with its precursor-mediated adsorption behavior, the surface reactivity of $Si_2H_6$ was found to be the highest on the unmodified Si(100)-$2{\times}1$ surface. This was correlated with its dissociative adsorption mechanism, in which both the $H_3Si-SiH_3$ bond scission and the dual surface $Si-SiH_3(a)$ bond formation require a surface dangling bond 'pair'. The unusually high thermal stability of $-SiH_3(a)$ on the unmodified surface was ascribed to a nearly close-packed $-SiH_3(a)$ coverage of ${\sim}0.9$ monolayer and the consequent lack of dangling bonds on the silyl-packed surface.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.322.1-322.1
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• 2014

Many research groups have studied tandem or multi-junction cells to overcome this low efficiency and degradation. In multi-junction cells, band-gap engineering of each absorb layer is needed to absorb the light at various wavelengths efficiently. Various absorption layers can be formed using multi-junctions, such as hydrogenated amorphous silicon carbide (a-SiC:H), amorphous silicon germanium (a-SiGe:H) and microcrystalline silicon (${\mu}c$-Si:H), etc. Among them, ${\mu}c$-Si:H is the bottom absorber material because it has a low band-gap and does not exhibit light-induced degradation like amorphous silicon. Nevertheless, ${\mu}c$-Si:H requires a much thicker material (>2 mm) to absorb sufficient light due to its smaller light absorption coefficient, highlighting the need for a high growth rate for productivity. ${\mu}c$-SiGe:H has a much higher absorption coefficient than ${\mu}c$-Si:H at the low energy wavelength, meaning that the thickness of the absorption layer can be decreased to less than half that of ${\mu}c$-Si:H. ${\mu}c$-SiGe:H films were prepared using 40 MHz very high frequency PECVD method at 1 Torr. SiH4 and GeH4 were used as a reactive gas and H2 was used as a dilution gas. In this study, the ${\mu}c$-SiGe:H layer for triple solar cells applications was performed to optimize the film properties.

• Journal of Sensor Science and Technology
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• v.1 no.1
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• pp.5-12
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• 1992

We have fabricated a-Si:H multilayer for contact-type linear image sensor by means of RF glow discharge decomposition method. The ITO/i-a-Si:H/Al structure has relatively high dark current due to indium diffusion and carrier injection from both electrodes, resulting in low photocurrent to dark current. To suppress the dark current and to enhance interface electric field between ITO and i-a-Si:H film we have fabricated ITO/insulator/i-a-S:H/p-a-S:H/Al multilayer film with blocking structure. The photocurrent of ITO/$SiO_{2}(300{\AA})$/i-a-Si:H/p-a-Si:H($1500{\AA}$)/Al multilayer sensor with 5V bias voltage became saturated at about 20nA under $20{\mu}W/cm^{2}$ light intensity, while the dark current was less than 0.1nA. To increase the light generation efficiency we have adopted ITO/$SiO_{x}N_{y}(300{\AA})$/i-a-Si:H/p-a-Si:H($1500{\AA}$)/Al structure, showing photocurrent of 30nA and dark current of 0.08nA with 5V bias voltage. Also the spectral photosensitivity of the multilayer was enhanced for short wavelength visible region of 560nm, compared with that of the a-Si:H monolayer of 630nm. And its photoresponse time was about 0.3msec with the film homogeneity of 5% deviation.

• Journal of the Korean Vacuum Society
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• v.6 no.S1
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• pp.59-65
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• 1997

Efficient Si(100) etching by thermal H atoms at low substrate temperatures has been achieved. Gas-phase etching product $SiH_4$(g) upon H atom bombardment resulting from direct abstraction of $SiH_3$(a) by impinging H atoms was detected with a quadrupole mass spectrometer over the substrate temperature range of 105-408 K Facile depletion of all surface silyl ($SiH_3$) groups the dissociative adsorption product of disilane ($Si_2H_6$) at 105K from Si(100)2$\times$1 by D atoms and continuous regeneration and removal of $SiD_3$(a) were all consumed. These results provide direct evidence for efficient silicon surface etching by thermal hydrogen bombardment at cryogenic temperatures as low as 105K We attribute the high etching efficiency to the formation and stability of $SiH_3$(a) on Si(100) at lowered surface temperatures allowing the $SiH_3$(a) abstraction reaction by additional H atom to produce $SiH_4$((g).

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.312-312
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• 2011

In SiH4/H2 discharge for growth process of hydrogenated amorphous silicon (a-Si:H), silane polymers, produced by SiH2 + Sin-1H2n ${\rightarrow}$ SinH2n+2, have no reactivity on the film-growing surface. However, under the SiH2 rich condition, high silane reactive species (HSRS) can be produced by electron collision to silane polymers. HSRS, having relatively strong reactivity on the surface, can react with dangling bond and form Si-H2 networks which have a close correlation with photo-induced degradation of a-Si:H thin film solar cell [1]. To find contributions of suggested several external plasma conditions (pressure, frequency and ratio of mixture gas) [2,3] to suppressing productions of HSRS, some plasma characteristics are studied by numerical methods. For this study, a zero-dimensional global model for SiH4/H2 discharge and a one-dimensional particle-in-cell Monte-Carlo-collision model (PIC-MCC) for pure SiH4 discharge have been developed. Densities of important reactive species of SiH4/H2 discharge are observed by means of the global model, dealing 30 species and 136 reactions, and electron energy probability functions (EEPFs) of pure SiH4 discharge are obtained from the PIC-MCC model, containing 5 charged species and 15 reactions. Using global model, SiH2/SiH3 values were calculated when pressure and driving frequency vary from 0.1 Torr to 10 Torr, from 13.56 MHz to 60 MHz respectively and when the portion of hydrogen changes. Due to the limitation of global model, frequency effects can be explained by PIC-MCC model. Through PIC-MCC model for pure SiH4, EEPFs are obtained in the specific range responsible for forming SiH2 and SiH3: from 8.75 eV to 9.47 eV [4]. Through densities of reactive species and EEPFs, polymerization reactions and production of HSRS are discussed.