Measurements of Light-Induced Degradation in A-Si, Ge:H, F Alloys,

1986 ◽  
Vol 70 ◽  
Author(s):  
J. Kolodzey ◽  
S. Aljishi ◽  
Z E. Smith ◽  
V. Chu ◽  
R. Schwarz ◽  
...  
Keyword(s):  
Activation Energy ◽  
Electronic Properties ◽  
Dark Conductivity ◽  
Narrow Gap ◽  
Conductivity Activation Energy ◽  
Optical And Electronic Properties ◽  
Amorphous Si

ABSTRACTThe effects of illumination on the optical and electronic properties of narrow gap hydrogenated and fluorinated amorphous Si-Ge (a-Si1-xGex:H, F) alloys have been evaluated. A series of alloys with optical gaps ranging from 1.30 eV to 1.64 eV has been light soaked at ∼1 sun intensity for 354 hours. Measurements of sub-gap absorption, photo- and dark conductivities and dark conductivity activation energy were made on alloys in the annealed and the light-soaked states. The results indicate that samples with optical gaps ≳ 1.4 eV degrade significantly. The 1.3 eV sample shows no degradation in its optical or electronic properties except for a factor of 5 increase in the dark conductivity.

Optical and electronic properties of amorphous SiNx:H alloy films

1985 ◽  
Vol 63 (6) ◽  
pp. 846-851 ◽  
Author(s):  
T. V. Herak ◽  
R. D. McLeod ◽  
M. G. Collett ◽  
K. C. Kao ◽  
H. C. Card ◽  
...  
Keyword(s):  
Nitrogen Content ◽  
Electronic Properties ◽  
Optical Excitation ◽  
Dark Conductivity ◽  
Dangling Bond ◽  
Alloy Films ◽  
Optical And Electronic Properties ◽  
Rf Glow Discharge ◽  
Gap States ◽  
Induced Changes

The optical and electronic properties of a-SiNx:H alloy films fabricated by rf glow discharge have been measured for 0 ≤ x ≤ 0.6. The material is dispersive over the range of photon energies 0.5 ≤ hv ≤ 3.5 eV. The optical gap is about 1.65 eV and is practically independent of x for 0.1 < x < 0.4, but it increases rapidly with increasing x for 0 < x < 0.1 and x > 0.4. For x > 0.6 the refractive index approaches the value for Si3N4. The dark conductivity, the photoconductivity, and the ratio of the photoconductivity to the dark conductivity are enhanced by nitrogen incorporation when appropriate nitrogen content is used. All the experimental results indicate that the incorporated nitrogen does not act as a dopant, but rather acts as a dangling-bond compensator. Photo-induced changes in both dark conductivity and photoconductivity due to high-intensity optical excitation have been observed. The degree of such changes decreases with increasing nitrogen content. This phenomenon is attributed to the photo-induced change in the microstructure of the films that leads to a change in both the density and the distribution of gap states.

Estimation of Defect State Densities from Bulk Photoelectronic Properties of a-Si,Ge:H Alloys

1987 ◽  
Vol 95 ◽  
Author(s):  
G. N. Parsons ◽  
G. Lucovsky
Keyword(s):  
Activation Energy ◽  
Incident Light ◽  
Film Surface ◽  
Dark Conductivity ◽  
State Density ◽  
Defect State ◽  
Oxide Interface ◽  
Conductivity Activation Energy ◽  
State Densities

AbstractWe have studied the photoelectronic properities of a- Si(x),Ge(1−x):H alloy films and have concluded that there are depletion layers at the film surface and film/oxide interface that effect the determination of bulk quantum effieciencymobility- lifetime (nuT) products. From changes in dark conductivity activation energy with film thickness and the nuT product with wavelength of incident light we have estimated defeci sta:e lensitles. Our best x=0.5 film has an nuT value of 9×10−8 cm2 V−1 andaj defect state density near the Fermi level of approximately 5×10 cm−3 eV−1.

Substrate Temperature Dependence of the Optical and Electronic Properties of Glow Discharge Produced a-Ge:H

1989 ◽  
Vol 149 ◽  
Author(s):  
Yuan- Min Li ◽  
Warren A. Turner ◽  
Choochon Lee ◽  
William Paul
Keyword(s):  
Glow Discharge ◽  
Substrate Temperature ◽  
Temperature Dependence ◽  
Electronic Properties ◽  
Dark Conductivity ◽  
Index Of Refraction ◽  
Atmospheric Contamination ◽  
Optical And Electronic Properties ◽  
Substrate Temperatures ◽  
Post Deposition

ABSTRACTGlow discharge a-Ge:H films produced at substrate temperatures (Tδ) between 50°C and 350°C, with and without a top a-Si:H capping layer, have been studied. The uncapped samples produced at Tδ < 250°C suffer severe post-deposition atmospheric contamination, resulting in orders of magnitude of unstable increase in both the photoresponse and dark conductivity. The capped samples, which have very much reduced immediate post-deposition contamination, show only small increases in the efficiency-mobility-lifetime product (ŋμτ) with increasing Tδ. This contrasts with the results of earlier similar studies on uncapped samples, which showed a peak in either the photoconductivity1 or the ratio of photoconductivity to dark conductivity2 for 150°C < Tδ < 2000C. We have also observed a decrease in the bandgap, a narrowing of the band-tails, an increase in the index of refraction, and a reduction of hydrogen content of the films with increasing Tδ.

Increasing The Dark Conductivity Activation Energy in Undoped Microcrystalline Silicon by Post-Growth Anneals

2001 ◽  
Vol 664 ◽  
Author(s):  
Jong-Hwan Yoon
Keyword(s):  
Activation Energy ◽  
Oxygen Concentration ◽  
Dark Conductivity ◽  
Low Energy ◽  
Microcrystalline Silicon ◽  
Conductivity Activation Energy ◽  
Constant Rate ◽  
Annealing Effects ◽  
Annealing Cycle ◽  
Type Character

ABSTRACTUndoped µc-Si:H film of the strong n-type character with the dark conductivity activation energy of about 0.28 eV was annealed. Annealing was carried out by slowly increasing the temperature from 25 °C to 450 °C at a constant rate of 12 °C/min (one annealing cycle). Annealing effects were monitored by measuring the changes in dark conductivity, oxygen and hydrogen concentrations, and photoluminescence (PL). Dark conductivity activation energy gradually increases with increasing the number of annealing cycles to a saturation value of about 0.6 eV. There is little or no change in the oxygen concentration, but the hydrogen concentration decreases with increasing the number of annealing cycles. The PL band near 1.2 eV disappears with annealing, while the low energy PL band near 0.85 eV dominates rather as the number of annealing cycles increases. A possible explanation will be discussed.

Intrinsic microcrystalline silicon by postgrowth anneals

2001 ◽  
Vol 16 (6) ◽  
pp. 1531-1534 ◽  
Author(s):  
Jong-Hwan Yoon
Keyword(s):  
Activation Energy ◽  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Dark Conductivity ◽  
Microcrystalline Silicon ◽  
Conductivity Activation Energy ◽  
High Hydrogen ◽  
Constant Rate ◽  
Annealing Cycle

Hydrogenated microcrystalline silicon (μc-Si:H) grown by a conventional plasma-enhanced chemical vapor deposition from high hydrogen-diluted silane was annealed by increasing the temperature from 25 to 450 °C at a constant rate of 12 °C/min (one annealing cycle). Dark-conductivity activation energy gradually increases with increasing the number of annealing cycle to a saturation value of about 0.6 eV, observed in truly intrinsic μc-Si:H films. For the saturated state, the dark conductivity of the order of 10−8 S/cm was obtained. Little or no change in the oxygen content was observed after the annealing.

Minority Carrier Diffusion Lengths And Photoconductivity In a-Si,N:H Deposited By Remote Pecvd

1994 ◽  
Vol 336 ◽  
Author(s):  
M.J. Williams ◽  
S.M. Cho ◽  
S.S. He ◽  
G. Lucovsky
Keyword(s):  
Activation Energy ◽  
Minority Carrier ◽  
Dark Conductivity ◽  
Wide Bandgap ◽  
Conductivity Ratio ◽  
Conductivity Activation Energy ◽  
Active Materials ◽  
Atom Source ◽  
Staebler Wronski Effect ◽  
Deposited Films

ABSTRACTWe have deposited films of a-Si,N:H by remote PECVD from N2 and SiH4 for N-concentrations, [N], to about 12 atomic percent (at. %). Bonded-H concentrations were ∼7–10 at. %, Mostly in Si-H groups. The films with [N] = 9–12 at. % have εθ4 bandgaps of ∼2.0 to 2.2 eV, which makes them potentially useful as wide bandgap photo-active materials in tandem PV cells. Several properties are of special interest for PV applications. First, like many other a-Si:H-based alloys, the photoconductivity relative to a-Si:H is degraded by alloying, but less than for a-Si,C:H alloys with the same bandgaps. Second, the ambipolar diffusion lengths (Ld) obtained with the Steady State Photocarrier Grating (SSPG) technique for films with [N] = 10 at. % and εθ4 = 2.1eV, are comparable to those of a-Si:H. For lightly-nitrided films to [N] ∼5 at. %, Ld first decreases with respect to a-Si:H and then increases as [N] increases from ∼7 at.% to 10–12 at. %. These trends follow the dark conductivity activation energy, Ea, which initially drops due to doping, and then increases into an alloy regime for [N] > 5 at. %. Films with [N1=10 at. % have dark conductivities and Ea's comparable to those of undoped a-Si:H. Third the magnitude of the Staebler-Wronski effect, as monitored by the photo- to dark conductivity ratio after a 1000 Minute lightsoak, was about the same as in a-Si:H. Finally, we contrast the properties of these films prepared from N2 with a-Si,N:H alloys with the same [N] and E04, but prepared from an ammonia N-atom source gas and attribute differences in their photoelectronic behavior such as a significantly enhanced Staebler-Wronski effect.to the presence of Si-NH bonding arrangements in the films grown from NH3.

Deposition and Characterization of Near “Intrinsic” μc-Si Films Deposited by Remote Plasma-Enhanced Chemical-Vapor Deposition - RPECVD

1991 ◽  
Vol 219 ◽  
Author(s):  
M. J. Williams ◽  
C. Wang ◽  
G. Lucovsky
Keyword(s):  
Activation Energy ◽  
Vapor Deposition ◽  
Room Temperature ◽  
Boron Concentration ◽  
Chemical Vapor ◽  
Dark Conductivity ◽  
Conductivity Activation Energy ◽  
Boron Doped ◽  
Si Films

ABSTRACTUndoped films of μc-Si deposited by RPECVD are n-type with a room temperature dark conductivity of ∼6×10-4 S/cm and an activation energy of ∼0.3 eV. This is due to native donor-like defects. We report on the conductivity and photoconductivity of boron-doped μc-Si, with emphasis on low doping levels that are designed to compensate exactly these native donor-like defects. We describe the dark conductivity and the photoconductivity as functions of dark conductivity activation energy and the average boron concentration, and present a model for the photoconductivity based on band off sets between the crystalline and amorphous regions of the μc-Si.

High Temperature n- and p-type Doped Microcrystalline Silicon Layers Grown by VHF PECVD Layer-by-Layer Deposition

2003 ◽  
Vol 762 ◽  
Author(s):  
A. Gordijn ◽  
J.K. Rath ◽  
R.E.I. Schropp
Keyword(s):  
Activation Energy ◽  
High Temperature ◽  
High Temperatures ◽  
Continuous Wave ◽  
Hydrogen Plasma ◽  
Silicon Layer ◽  
Dark Conductivity ◽  
High Deposition Rate ◽  
Layer By Layer ◽  
Microcrystalline Silicon

AbstractDue to the high temperatures used for high deposition rate microcrystalline (μc-Si:H) and polycrystalline silicon, there is a need for compact and temperature-stable doped layers. In this study we report on films grown by the layer-by-layer method (LbL) using VHF PECVD. Growth of an amorphous silicon layer is alternated by a hydrogen plasma treatment. In LbL, the surface reactions are separated time-wise from the nucleation in the bulk. We observed that it is possible to incorporate dopant atoms in the layer, without disturbing the nucleation. Even at high substrate temperatures (up to 400°C) doped layers can be made microcrystalline. At these temperatures, in the continuous wave case, crystallinity is hindered, which is generally attributed to the out-diffusion of hydrogen from the surface and the presence of impurities (dopants).We observe that the parameter window for the treatment time for p-layers is smaller compared to n-layers. Moreover we observe that for high temperatures, the nucleation of p-layers is more adversely affected than for n-layers. Thin, doped layers have been structurally, optically and electrically characterized. The best n-layer made at 400°C, with a thickness of only 31 nm, had an activation energy of 0.056 eV and a dark conductivity of 2.7 S/cm, while the best p-layer made at 350°C, with a thickness of 29 nm, had an activation energy of 0.11 V and a dark conductivity of 0.1 S/cm. The suitability of these high temperature n-layers has been demonstrated in an n-i-p microcrystalline silicon solar cell with an unoptimized μc-Si:H i-layer deposited at 250°C and without buffer. The Voc of the cell is 0.48 V and the fill factor is 70 %.

1,1’-Biaceanthrylene and 2,2'-Biaceanthrylene: Models for Linking Larger Polycyclic Aromatic Hydrocarbons via Five-Membered Rings

2019 ◽  
Author(s):  
Yachu Du ◽  
Kyle Plunkett
Keyword(s):  
Polycyclic Aromatic Hydrocarbons ◽  
Polycyclic Aromatic Hydrocarbon ◽  
Aromatic Hydrocarbon ◽  
Electronic Properties ◽  
Aromatic Hydrocarbons ◽  
Model Systems ◽  
Redox Potentials ◽  
Dimer Model ◽  
Optical And Electronic Properties ◽  
Polycyclic Aromatic

We show that polycyclic aromatic hydrocarbon (PAH) chromophores that are linked between two five-membered rings can access planarized structures with reduced optical gaps and redox potentials. Two aceanthrylene chromophores were connected into dimer model systems with the chromophores either projected outward (2,2’-biaceanthrylene) or inward (1,1’-biaceanthrylene) and the optical and electronic properties were compared. Only the planar 2,2’-biaceanthrylene system showed significant reductions of the optical gaps (1 eV) and redox potentials in relation to the aceanthrylene monomer.<br>

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