Effects of Chlorine on Dopant Activation in a-Si:H

1999 ◽  
Vol 557 ◽  
Author(s):  
Adam M. Payne ◽  
Sigurd Wagner
Keyword(s):  
Gas Phase ◽  
Hydrogenated Amorphous Silicon ◽  
Dark Conductivity ◽  
Rf Plasma ◽  
Dopant Activation ◽  
Dc Discharge ◽  
Order Of Magnitude ◽  
P Type ◽  
Phosphorus Doped ◽  
Hydrogenated Amorphous

AbstractThe incorporation of chlorine has a significant effect on the dark conductivity of doped and undoped hydrogenated amorphous silicon (a-Si:H). The dark conductivity of a-Si:H films deposited from dichlorosilane (SiCl2H2) and SiH4, and doped with diborane, increases by as much as a factor of 100 over the usual a-Si:H,B films deposited without SiCl2H2. The effect is observed at gas phase concentrations of diborane ranging from 0.006% to 0.5%, and for both DC and RF plasma depositions, although it is more noticeable for the DC discharge. An increase in dark conductivity is also observed in B doped a-Si,C:H films deposited with dichlorosilane, albeit coupled with a change in the Tauc gap. Chlorine reduces the conductivity of undoped and phosphorus doped a-Si:H films. Undoped a-Si:H films deposited from SiCl2H2 and SiH4 have a dark conductivity of ~1. 10-12 S.cm-1, which is an order of magnitude lower than films deposited from pure SiH4. We discuss several alternatives for the mechanism of chlorine enhanced or reduced dopant activation. We have made solar cells using chlorinated p-type a-SiC:H films as the p-layers.

Boron doping in a-SiO:H,

2014 ◽  
Vol 92 (7/8) ◽  
pp. 586-588 ◽  
Author(s):  
Y. Kitani ◽  
T. Maeda ◽  
S. Kakimoto ◽  
K. Tanaka ◽  
R. Okumoto ◽  
...  
Keyword(s):  
Amorphous Silicon ◽  
Hydrogenated Amorphous Silicon ◽  
Hole Mobility ◽  
Boron Doping ◽  
Type A ◽  
Dark Conductivity ◽  
Wide Range ◽  
P Type ◽  
Hydrogenated Amorphous ◽  
Silicon Oxygen

Boron-doping characteristics in hydrogenated amorphous silicon–oxygen alloys (a-SiO:H) have been studied in contrast to those in hydrogenated amorphous silicon (a-Si:H). Although the boron-incorporation efficiency shows almost the same value between a-SiO:H and a-Si:H, p-type a-SiO:H (p-a-SiO:H) exhibits lower dark conductivity by one or two orders of magnitude as compared to p-type a-Si:H (p-a-Si:H) in a wide range of doping levels. We have found that p-a-SiO:H exhibits low dark conductivity as compared to p-a-Si:H even when we choose samples showing the same activation energy from a variety of as-deposited and thermally annealed samples. We have concluded from the different Urbach-energy values between high quality intrinsic a-SiO:H and a-Si:H that the origin of low dark conductivity in p-a-SiO:H is due to low hole mobility.

Light Induced Effects in A-Si:H Films Alloyed with Sulfur

1997 ◽  
Vol 467 ◽  
Author(s):  
Jong-Hwan Yoon ◽  
P. C. Taylor ◽  
Baojie Yan ◽  
Czang-Ho Lee
Keyword(s):  
Defect Density ◽  
Hydrogenated Amorphous Silicon ◽  
Dark Conductivity ◽  
Gas Mixture ◽  
Small Decrease ◽  
Illumination Time ◽  
Spin Resonance ◽  
Photo Conductivity ◽  
Order Of Magnitude ◽  
Hydrogenated Amorphous

ABSTRACTLight-induced effects are studied in hydrogenated amorphous silicon-sulfur alloys (a-SiSx:H) and compared to those that exist in a-Si:H. The a-SiSx:H films were grown by decomposition of pre-mixtures of SiH4 and H2 S. The light-induced effects were monitored using electrical (dark conductivity and photoconductivity, including the constant photocurrent method [CPM]) and optical (photoluminescence) measurements and electron spin resonance. It is found that sulfur alloying results in a significant reduction in the degradation in the dark- and photo-conductivity. For ana-SiSx:H film grown with a gas mixture of H2 S/SiH4= 0.02, there is an increase of over an order of magnitude in the dark conductivity and a small decrease in the photoconductivity after 50 hours of light soaking. The subgap deep defect density as measured by CPM increases with illumination time, following a stretched exponential to saturation. The saturated defect density is an order of magnitude higher than that observed in the annealed state.

The Potential of Hydrogenated Amorphous Silicon-Sulfur Alloys for Absorber Materials in Photovoltaic Devices

1996 ◽  
Vol 426 ◽  
Author(s):  
P. C. Taylor ◽  
S. L. Wang
Keyword(s):  
Amorphous Silicon ◽  
Hydrogenated Amorphous Silicon ◽  
Optical Excitation ◽  
Dark Conductivity ◽  
General Idea ◽  
Group Vi ◽  
Excitation Light ◽  
Staebler Wronski Effect ◽  
P Type ◽  
Hydrogenated Amorphous

AbstractThe group VI element, sulfur, is an inefficient donor in hydrogenated amorphous silicon (a-Si:H). The compensation by sulfur donors of the p-type conductivity obtained with diborane in a-Si:H provides additional evidence of the role of sulfur as a donor. By adding equal amounts of diborane and hydrogen sulfide in the plasma the dark conductivity at room temperature can be reduced by one to two orders of magnitude compared to the corresponding p-type a-Si:H with the same boron concentration. Unlike phosphorus doping, a portion of the sulfur-related donors is passivated by hydrogen in the annealed state. This passivated portion can be rendered electrically active by optical excitation. This effect is similar to that which has been called persistent photoconductivity (PPC) and occurs in some compensated samples of a-Si:H and in some multilayer structures. The PPC effect has the opposite effect on both the photo- and dark conductivities from the Staebler-Wronski effect. For this reason it is possible to find an appropriate S/Si ratio where the two effects cancel as far as the conductivity is concerned. For an appropriate concentration of S in “intrinsic” a-Si:H one can obtain samples with high photoconductivity and essentially no degradation in either the dark or the photo-conductivities upon prolonged optical excitation (light soaking). These results suggest that at least the majority carriers are unaffected; however, it remains unclear what effect this second metastability will have on the minority carriers, and hence on PV device applications. The general idea that the addition of a second metastability to hydrogenated amorphous silicon (a-Si:H) might counteract the deleterious consequences of the Staebler-Wronski effect is presented.

Stability of hydrogenated amorphous silicon prepared by reactive evaporation

1991 ◽  
Vol 69 (6) ◽  
pp. 679-683
Author(s):  
D. C. Craigen ◽  
R. D. Audas ◽  
D. E. Brodie
Keyword(s):  
Activation Energy ◽  
Amorphous Silicon ◽  
Hydrogenated Amorphous Silicon ◽  
Dark Conductivity ◽  
Time Curve ◽  
Switching Model ◽  
Order Of Magnitude ◽  
Reactive Gases ◽  
Staebler Wronski Effect ◽  
Hydrogenated Amorphous

Hydrogenated amorphous silicon (a-Si:H) was prepared by evaporating Si in a controlled ambient of reactive gases. Contamination of the samples by exposure to air affects both the dark conductivity and the photoconductivity. Some of the contamination effects can be removed by annealing, but some changes are not reversible. The irreversible changes are mainly due to the chemisorption of oxygen obtained from water vapour when the samples are stored in air. The Staebler–Wronski effect is observed in all samples whose photoconductivity is at least an order of magnitude higher than the dark conductivity. The photoconductivity versus time curve displays at t−1/3 dependence, typical of the Staebler–Wronski effect, but the degradation is much slower than that reported for glow discharge a-Si:H. The activation energy for the effect is 0.12 eV, which is larger than the 0.04 eV expected for the bond-switching model.

The Potential of Hydrogenated Amorphous Silicon-Sulfur Alloys for Absorber Materials in Photovoltaic Devices

1996 ◽  
Vol 420 ◽  
Author(s):  
P. C. Taylor ◽  
S. L. Wang
Keyword(s):  
Amorphous Silicon ◽  
Hydrogenated Amorphous Silicon ◽  
Optical Excitation ◽  
Dark Conductivity ◽  
General Idea ◽  
Group Vi ◽  
Excitation Light ◽  
Staebler Wronski Effect ◽  
P Type ◽  
Hydrogenated Amorphous

AbstractThe group VI element, sulfur, is an inefficient donor in hydrogenated amorphous silicon (a-Si:H). The compensation by sulfur donors of the p-type conductivity obtained with diborane in a-Si:H provides additional evidence of the role of sulfur as a donor. By adding equal amounts of diborane and hydrogen sulfide in the plasma the dark conductivity at room temperature can be reduced by one to two orders of magnitude compared to the corresponding p-type a-Si:H with the same boron concentration. Unlike phosphorus doping, a portion of the sulfur-related donors is passivated by hydrogen in the annealed state. This passivated portion can be rendered electrically active by optical excitation. This effect is similar to that which has been called persistent photoconductivity (PPC) and occurs in some compensated samples of a-Si:H and in some multilayer structures. The PPC effect has the opposite effect on both the photo- and dark conductivities from the Staebler-Wronski effect. For this reason it is possible to find an appropriate S/Si ratio where the two effects cancel as far as the conductivity is concerned. For an appropriate concentration of S in “intrinsic” a-Si:H one can obtain samples with high photoconductivity and essentially no degradation in either the dark or the photo-conductivities upon prolonged optical excitation (light soaking). These results suggest that at least the majority carriers are unaffected; however, it remains unclear what effect this second metastability will have on the minority carriers, and hence on PV device applications. The general idea that the addition of a second metastability to hydrogenated amorphous silicon (a-Si:H) might counteract the deleterious consequences of the Staebler-Wronski effect is presented.

Effects of Fluorine Implantation into Hydrogenated Amorphous Silicon

1991 ◽  
Vol 235 ◽  
Author(s):  
S. P. Wong ◽  
Shaoqi Peng ◽  
Ning Ke ◽  
Jingxi Liu
Keyword(s):  
Amorphous Silicon ◽  
Spin Density ◽  
Hydrogenated Amorphous Silicon ◽  
Dark Conductivity ◽  
Fluorine Concentration ◽  
Electrical Measurements ◽  
Large Shift ◽  
Before And After ◽  
Order Of Magnitude ◽  
Hydrogenated Amorphous

ABSTRACTMultiple-energy implantation of fluorine into rf glow discharge deposited hydrogenated amorphous silicon (a-Si:H) thin films has been performed. It is found that the optical gap decreases with the implanted fluorine concentration CF from 1.56 eV for the unimplanted sample to 1.40 eV for the sample with CF of 3×1021 cm−3. Results of the Staebler-Wronski experiment show that the ratio between the electrical conductivity before and after illumination, as well as the ratio between the photo- and dark conductivity, decrease also with Cp. Electrical measurements show that there is significant decrease in the conductivity activation energy Ea with CF for samples annealed at or below the substrate temperature TS during deposition. But for samples annealed at temperatures higher than TS, Ea was found to change back to values close to that of the unimplanted sample. A large shift to higher energy for one peak in the photoluminescence spectra at 77K has been observed, from 1.34 eV of the unimplanted sample to around 1.6 eV for the implanted samples, though with almost one order of magnitude weakening in intensity. It is also observed that ESR splitting has been induced in the fluorine implanted samples. The g-factors of the two resonances are determined to be 2.003 and 2.006, respectively. For the g=2.006 resonance, the spin density increases markedly after implantation but is essentially independent on CF before annealing and effectively reduced or eliminated after annealing. For the g=2.003 resonance, the spin density increases rapidly with CFp especially in the range from CF = 1×1020 to 1×1021 cm−3 before annealing and reduces only slightly after annealing.

Light-Induced Effects on Fluorinated Amorphous and Microcrystalline Silicon Films

1996 ◽  
Vol 420 ◽  
Author(s):  
Hong-Seok Choi ◽  
Keun-Ho Jang ◽  
Jhun-Suk Yoo ◽  
Min-Koo Han
Keyword(s):  
Band Gap ◽  
Vapor Deposition ◽  
Optical Band Gap ◽  
Silicon Film ◽  
Hydrogenated Amorphous Silicon ◽  
Chemical Vapor ◽  
Rf Plasma ◽  
Microcrystalline Silicon ◽  
Amorphous Silicon Film ◽  
Hydrogenated Amorphous

AbstractThe fluorinated amorphous and microcrystalline silicon (a,μc-Si:H;F) films have been prepared by rf plasma enhanced chemical vapor deposition (PECVD) with SiH 4 and SiF 4 gas mixtures. The stretching Si-O (1085 cm-1) and SiH2 (2100 cm-1) bands estimated from infrared (IR) spectroscope data have related to the evolution of crystallinity and the optical band gap was shifted by introducing Si-O bonds. The sub-band gap absorption coefficient in a,μc-Si:H;F films was about one order lower than that in hydrogenated amorphous silicon film (a-Si:H). The subband gap absorption in a-Si:H;F film was comparable to that in tic-Si:H;F films. The lightinduced degradation of a,μc-Si:H;F films were also suppressed.

scholarly journals Defect Frozen Phenomena in Phosphorus-Doped Hydrogenated Amorphous Silicon

1989 ◽  
Vol 97 (1127) ◽  
pp. 699-705
Author(s):  
Yukio OSAKA ◽  
Hiroyuki NASU ◽  
Chikashi AKAMATSU ◽  
Ryo HAYASHI
Keyword(s):  
Amorphous Silicon ◽  
Hydrogenated Amorphous Silicon ◽  
Phosphorus Doped ◽  
Hydrogenated Amorphous
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