Structural and Electronic Properties of Hydrogenated Nanocrystalline Silicon Films Made with Hydrogen Dilution Profiling Technique

2005 ◽  
Vol 862 ◽  
Author(s):  
Keda Wang ◽  
Daxing Han ◽  
D. L. Williamson ◽  
Brittany Huie ◽  
J. R. Weinberg-Wolf ◽  
...  
Keyword(s):  
Electronic Properties ◽  
Volume Fraction ◽  
Nanocrystalline Silicon ◽  
Growth Direction ◽  
Structure Evolution ◽  
Excitation Wavelength ◽  
Initial Growth ◽  
High Hydrogen ◽  
Hydrogen Dilution ◽  
Structural And Electronic Properties

AbstractWe used X-ray diffraction (XRD), Raman scattering and photoluminescence (PL) spectroscopy to characterize structural and electronic properties of nc-Si:H films made with different hydrogen dilution ratios and hydrogen dilution profiling with continuously reduced hydrogen dilution during the deposition. The XRD results show that the crystalline volume fraction (fc) is in the range of 60-70% with grain size of 22-26 nm for the nc-Si:H films studied. Comparing the sample made using hydrogen dilution profiling to that with constant hydrogen dilution, the hydrogen dilution profiling promotes the (220) preferential orientation due to a very high hydrogen dilution in the initial growth. The Raman results show that the fc is in the range of 60-90%, depending on the sample and excitation wavelength. For the samples with constant hydrogen dilution, the fc measured by Raman increases along the growth direction. The hydrogen dilution profiling reverses this trend, which affirms that the hydrogen profiling controls the nanocrystalline structure evolution along the growth direction. The PL results show only one peak around 0.8-0.9 eV for the samples made with constant hydrogen dilution, but an additional peak at 1.4 eV appears in the sample made with the hydrogen dilution profiling.

Microcrystalline Germanium Photodetectors

2001 ◽  
Vol 664 ◽  
Author(s):  
M. Krause ◽  
H. Stiebig ◽  
R. Carius ◽  
H. Wagner
Keyword(s):  
Electronic Properties ◽  
Near Infrared ◽  
Short Circuit ◽  
Chemical Vapor ◽  
Short Circuit Current ◽  
Infrared Light ◽  
High Hydrogen ◽  
Sensor Applications ◽  
Hydrogen Dilution ◽  
Structural And Electronic Properties

ABSTRACTFor sensor applications in the detection of near infrared light we have prepared μc-Ge:H by plasma enhanced chemical vapor deposition (PECVD) with a mixture of germane and hydrogen, investigatedits structural and electronic properties and incorporated it into thin pin diodes. In order to ensure microcrystalline growth we had to use high hydrogen dilution. However, only the material prepared with a ratio of germane to hydrogen of 0.2% shows high crystallinity. The optical absorption is remarkably different from c-Ge and exhibits no indication of a direct gap at 0.8eV. When this material is implemented as part of a 110nm thin absorber, a short circuit current of 20mA/cm2 and a quantum efficiency of 15% at a wavelength of 1.1μm are achieved. Higher germane concentrations in hydrogen lead to poor electronic properties due to an increase of the amorphous phase and the short circuit current of the devices deteriorates. As for crystalline germanium photodiodes cooling of the devices is used to overcome the restrictionoriginating from the high free carrier concentration.

Hot-Wire CVD Poly-Silicon Films for Thin Film Devices

1998 ◽  
Vol 507 ◽  
Author(s):  
J.K. Rath ◽  
F.D. Tichelaar ◽  
H. Meiling ◽  
R.E.I. Schropp
Keyword(s):  
Defect Density ◽  
Initial Growth ◽  
Oriented Growth ◽  
Compact Structure ◽  
High Hydrogen ◽  
New Approach ◽  
Intrinsic Nature ◽  
Bias Stress ◽  
Hydrogen Dilution ◽  
Long Duration

ABSTRACTSolar cell using profiled poly-Si:H by HWCVD as i-layer in the configuration SS/n-µSi:H(PECVD)/i-poly-Si:H(HWCVD)/p-µc-Si:H(PECVD)/ITO showed 3.7% efficiency. A current of 23.6 mA/cm2 was generated in only 1.5 µm thick poly-Si:H i-layer grown at ∼5Å/s. TFTs made with the poly-Si:H films (grown at ≥ 9Å/s) exhibited remarkable stability to long duration of 23 hours of gate bias stress of ∼lMV/cm. A saturation mobility of 1.5 cm2/Vs for the TFT has been achieved. Films made at low hydrogen dilution (Poly2) showed device quality (purely intrinsic nature, ambipolar diffusion length of 568 nm, only (220) oriented growth and low ESR defect density of <1017/cm3with complete absence of signal due to conduction electrons) but with an incubation phase of amorphous initial growth, whereas the films made at high hydrogen dilution (Polyl) had a polycrystalline initial growth, though with higher defect density, incorporated oxygen and randomly oriented grains. Poly2 films are compact and hydrogen bonding is at compact Si-H sites manifested as 2000 cm−1IR vibration and high temperature hydrogen evolution peak. Exchange interaction of spins and spin pairing are observed while increasing defects in such a compact structure. A new approach has been used to integrate these two regimes of growth to make profiled poly-Si:H layers. The new layers show good electronic properties as well as complete elimination of incubation phase.

Research on Nanocrystalline Silicon Film Solar Cells

2011 ◽  
Vol 347-353 ◽  
pp. 870-873
Author(s):  
Chun Rong Xue
Keyword(s):  
Grain Size ◽  
Solar Cells ◽  
Band Gap ◽  
Optical Band Gap ◽  
Volume Fraction ◽  
Silicon Film ◽  
Nanocrystalline Silicon ◽  
Processing Parameters ◽  
Crystalline Volume Fraction ◽  
Hydrogen Dilution

Nanocrystalline silicon film has become the research hit of today’ s P-V solar technology. It’s optical band gap was controlled through changing the grain size and crystalline volume fraction for the quanta dimension effect. The crystalline volume fraction in nc-Si:H is modulated by varying the hydrogen concentration in the silane plasma. Also, the crystallinity of the material increases with increasing hydrogen dilution ratio, the band tail energy width of the nc-Si:H concurrently decreases. Two sets of nc-Si:H solar cells were made with different layer thicknesss, their electronic and photonic bandgap, absorption coefficient, optical band gap, nanocrystalline grain size(D), and etc have been stuied. In addition, we discussed the relationship between the stress of nc-Si thin films and H2 ratio. At last nc-Si:H solar cells have been designed and prepared successfully in the optimized processing parameters.

scholarly journals Influence of Hydrogen Dilution of Silane on the Properties of nc-Si:H Films Grown by Layer-by-Layer Deposition Technique

2007 ◽  
Vol 31 ◽  
pp. 80-82 ◽  
Author(s):  
Goh Boon Tong ◽  
Siti Meriam Ab. Gani ◽  
Saadah Abdul Rahman
Keyword(s):  
Raman Scattering ◽  
Energy Gap ◽  
Nanocrystalline Silicon ◽  
Flow Rate Ratio ◽  
Layer By Layer ◽  
Deposition Technique ◽  
Crystal Silicon ◽  
High Hydrogen ◽  
Nanocrystallite Size ◽  
Hydrogen Dilution

Hydrogenated nanocrystalline silicon (nc-Si:H) films produced by layer-by-layer (LBL) deposition technique were studied. The films were grown at different hydrogen to silane flow-rate ratio on crystal silicon (111) substrate. The properties of films were investigated by X-ray diffraction (XRD), micro-Raman scattering spectroscopy, Fourier transform infrared (FTIR) spectroscopy, optical transmission spectroscopy, atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM). These properties showed dependence on the hydrogen dilution of silane. Appearance of XRD peaks at diffraction angles of 28.4 o and 56.1 o which correspond to silicon orientation of (111) and (311) respectively, were observed in all films indicating evidence of crystallinity in the films. Raman scattering results indicated that crystallinity in the films was due to the presence of nanocrystallites embedded in an amorphous matrix. The energy gap of the films showed dependence on the hydrogen content in the films. Increase in nanocrystallite size resulted in increase in disorder at low hydrogen dilution films but films remain homogenous with increase in nanocrystallite size for the high hydrogen dilution films.

Evolution of Structural and Electronic Properties in Boron-doped Nanocrystalline Silicon Thin Films

2007 ◽  
Vol 989 ◽  
Author(s):  
Hyun Jung Lee ◽  
Andrei Sazonov ◽  
Arokia Nathan
Keyword(s):  
Electronic Properties ◽  
Chemical Vapor ◽  
Boron Doping ◽  
Nanocrystalline Silicon ◽  
Dark Conductivity ◽  
Crystalline Fraction ◽  
Silicon Thin Films ◽  
Boron Doped ◽  
Structural And Electronic Properties ◽  
Effective Mobility

AbstractWe report on the boron-doping dependence of the structural and electronic properties in nanocrystalline silicon (nc-Si:H) films directly deposited by plasma- enhanced chemical vapor deposition (PECVD). The crystallinity, micro-structure, and dark conductivity of the films were investigated by gradually varying the ratio of trimethylboron [B(CH3)3 or TMB] to silane (SiH4) from 0.1 to 2 %. It was found that the low level of boron doping (< 0.2 %) first compensated the nc-Si:H material which demonstrates slightly n-type properties. As the doping increased up to 0.5 %, the maximum dark conductivity (ód) of 1.11 S/cm was obtained while high crystalline fraction (Xc) of the films (over 70 %) was maintained. However, further increase in a TMB-to-SiH4 ratio reduced ód to the order of 10-7 S/cm due to a phase transition of the films from nanocrystalline to amorphous, which was indicated by Raman spectra measurements.P-channel nc-Si:H thin film transistors (TFTs) with top gate and staggered source/drain contacts were fabricated using the developed p+ nc-Si:H layer. The fabricated TFT exhibits a threshold voltage (VTp) of -26.2 V and field effective mobility of holes (μp) of 0.24 cm2/V·s.

The Effects of Hydrogen Profiling and of Light-Induced Degradation on the Electronic Properties of Hydrogenated Nanocrystalline Silicon

2005 ◽  
Vol 862 ◽  
Author(s):  
A.F. Halverson ◽  
J.J. Gutierrez ◽  
J.D. Cohen ◽  
Baojie Yan ◽  
Jeffrey Yang ◽  
...  
Keyword(s):  
Electronic Properties ◽  
Minority Carrier ◽  
Defect Density ◽  
Light Exposure ◽  
Nanocrystalline Silicon ◽  
Drive Level ◽  
Dramatic Decrease ◽  
Transient Photocurrent ◽  
Hydrogen Dilution ◽  
Carrier Collection

AbstractThe electronic properties of hydrogenated nanocrystalline silicon (nc-Si:H) were studied using junction capacitance methods. Drive-level capacitance profiling (DLCP) measurements revealed significant differences for nc-Si:H layers deposited under constant hydrogen dilution compared to those deposited using hydrogen profiling, with lower DLCP densities in the latter case. Transient photocapacitance (TPC) measurements revealed the mixed-phase nature of these materials. It disclosed spectra that appeared quite microcrystalline-like at lower temperatures, but more similar to a-Si:H at higher temperatures where the minority carrier collection is higher in the nanocrystalline component of these samples. This then suppresses the TPC signal from this component compared to the a-Si:H component. In contrast, because transient photocurrent signals are enhanced by the additional minority carrier collection, those spectra appear microcrystalline like at all temperatures. We also investigated the effects of light-induced degradation in these devices. This caused a dramatic decrease in hole collection, similar to that caused by reducing the measurement temperature of the samples. However, the light exposure did not appear to increase the deep defect density (dangling bonds).

Metastability in hydrogenated nanocrystalline silicon solar cells

2007 ◽  
Vol 22 (5) ◽  
pp. 1128-1137 ◽  
Author(s):  
Guozhen Yue ◽  
Baojie Yan ◽  
Gautam Ganguly ◽  
Jeffrey Yang ◽  
Subhendu Guha
Keyword(s):  
Solar Cells ◽  
Band Gap ◽  
Amorphous Phase ◽  
Reverse Bias ◽  
Volume Fraction ◽  
Nanocrystalline Silicon ◽  
Silicon Solar Cells ◽  
Single Junction ◽  
Hydrogen Dilution ◽  
Forward Current

Light-induced metastability in hydrogenated nanocrystalline silicon (nc-Si:H) single-junction solar cells was studied systematically. First, we observed no light-induced degradation when the photon energy was lower than the band gap of the amorphous phase; degradation occurred when the energy was higher than the band gap in the amorphous phase. The light-induced degradation could be annealed away at an elevated temperature. We concluded that the light-induced defect generation occurred mainly in the amorphous phase. Second, forward current injection did not degrade the nc-Si:H cell performance. However, a reverse bias during light soaking enhanced the degradation. Third, the nc-Si:H cells made with an optimized hydrogen dilution profile showed minimal degradation although these cells had a high amorphous volume fraction. This indicated that the amorphous volume fraction was not the only factor determining the degradation. Other factors also played important roles in the nc-Si:H stability.

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