Efficient Visible Room Temperature Photoluminescence in Wide Gap Hydrogenated Amorphous Silicon-Carbon Alloys

1994 ◽  
Vol 336 ◽  
Author(s):  
Leandro R. Tessler ◽  
Ionel Solomon
Keyword(s):  
Room Temperature ◽  
Urbach Energy ◽  
Photoluminescence Intensity ◽  
Tetrahedral Coordination ◽  
Hydrogenated Silicon ◽  
Amorphous Hydrogenated Silicon ◽  
Silicon Carbon ◽  
Hydrogenated Amorphous ◽  
Carbon Concentrations ◽  
Phonon Model

ABSTRACTWe report a photoluminescence study on amorphous hydrogenated silicon carbon (a-Si1-xCx:H) alloys with carbon concentration in the range O < x < 0.5, prepared by PECVD in the “low-power” regime, that preserves the tetrahedral coordination of the carbon atoms. These samples have optical gaps higher than conventional “high power” alloys with the same carbon content. For carbon concentrations below x = 0.2 the photoluminescence behaves essentially as in pure a-Si:H with increased gap, Urbach energy and DOS. For higher carbon concentrations there is a change in the recombination process, that we attribute to a change in the dominating diffusion process of the photogenerated carriers. The integrated photoluminescence intensity for carbon-rich samples is very weakly dependent on the temperature, and at room temperature it approaches that of pure a-Si:H at 77K. For all samples, the photoluminescence bandwidth can be well described by a zero-phonon model.

Room Temperature Light Induced Electron Spin Resonauce In Undoped Hydrogenated Amorphous Silicon (a-Si:H)

1986 ◽  
Vol 70 ◽  
Author(s):  
R. Pandya ◽  
S. Zafar ◽  
E. A. Schiff
Keyword(s):  
Electron Spin ◽  
Room Temperature ◽  
Small Shift ◽  
Hydrogenated Silicon ◽  
Transient Photocurrent ◽  
Amorphous Hydrogenated Silicon ◽  
Spin Resonance ◽  
Absorption Studies ◽  
G Value ◽  
Hydrogenated Amorphous

ABSTRACTThe effects of illumination upon the absorption electron spin resonance spectrum of the dangling bond defect system have been studied in undoped amorphous hydrogenated silicon (a-Si:H). A small shift of the inhomogeneous envelope of the system towards higher g-value is observed at roomtemperature. The shift is not accompanied by a significant change in the signal. Results are reported which indicate that this shift is not due to illumination induced heating of the specimen or calibration changes of the spectrometer. The results may be related to previously reported optical bias effects upon transient photocurrent and photoinduced absorption studies.

Porous Silicon from Hydrogenated Amorphous Silicon: Comparison with Crystalline Porous Silicon

1996 ◽  
Vol 452 ◽  
Author(s):  
J.-N. Chazalviel ◽  
R. B. Wehrspohn ◽  
I. Solomon ◽  
F. Ozanam
Keyword(s):  
Porous Silicon ◽  
Room Temperature ◽  
Quantum Confinement Effect ◽  
Confinement Effect ◽  
High Resistivity ◽  
Hydrogenated Silicon ◽  
Boron Doped ◽  
Amorphous Hydrogenated Silicon ◽  
Recombination Centers ◽  
Hydrogenated Amorphous

AbstractDevice-grade, boron-doped amorphous hydrogenated silicon can be made microporous by anodization in ethanoic HF. The thickness of the porous layer is limited by an instability due to the high resistivity of the material. Amorphous porous silicon exhibits strong room-temperature photoluminescence around 1.5 eV even in samples containing a high density of non-radiative recombination centers. This demonstrates the presence of a spatial confinement effect, as opposed to quantum confinement effect for crystalline porous silicon. The temperature dependence of the luminescence intensity is also accounted for on the same grounds.

Sputtered Fitas of Amorphous Hydrogenated Silicon Carbide

1987 ◽  
Vol 97 ◽  
Author(s):  
Richard B. Rizk ◽  
Alain E. Kaloyeros ◽  
Wendell S. Williams ◽  
Nancy Finnegan ◽  
Carol Kozlowski
Keyword(s):  
Structural Changes ◽  
Rapid Development ◽  
Chemical Bonds ◽  
Complete Understanding ◽  
Silicon Matrix ◽  
Hydrogenated Silicon ◽  
Physical Mechanisms ◽  
Amorphous Hydrogenated Silicon ◽  
Silicon Carbon ◽  
Scientific Attention

The field of amorphous hydrogenated silicon-carbon alloys and thin films has witnessed, since the pioneering work of Anderson and Spear [1], rapid development and has attracted scientific attention and technological interest [2,3]. However, relatively little information is known [4] about the physical mechanisms that govern the inclusion of C and H in the silicon matrix, the nature of the chemical bonds involved, and the structural changes that result in the amorphous phase. Clearly, further fundamental studies are needed to achieve complete understanding of such amorphous systems with variable disorder.

Room-temperature electroluminescence from erbium-doped amorphous hydrogenated silicon

1998 ◽  
Vol 80 (1-4) ◽  
pp. 335-338 ◽  
Author(s):  
O.B Gusev ◽  
M.S Bresler ◽  
E.I Terukov ◽  
K.D Tsendin ◽  
I.N Yassievich
Keyword(s):  
Room Temperature ◽  
Hydrogenated Silicon ◽  
Amorphous Hydrogenated Silicon ◽  
Erbium Doped

Saturation behavior of the Light-Induced Defect Density in Hydrogenated Amorphous Silicon

1990 ◽  
Vol 192 ◽  
Author(s):  
H. R. Park ◽  
J. Z. Liu ◽  
P. Roca i Cabarrocas ◽  
A. Maruyama ◽  
M. Isomura ◽  
...  
Keyword(s):  
Amorphous Silicon ◽  
Room Temperature ◽  
Urbach Energy ◽  
Defect Density ◽  
Generation Rate ◽  
Carrier Generation ◽  
Defect Generation ◽  
Ion Laser ◽  
Hydrogenated Amorphous ◽  
Defect Densities

ABSTRACTUsing a Kr ion laser (λ = 647.1 nm) to produce a carrier generation rate G of 3 × 1020 cm−3s−1, we have saturated the light-induced defect generation in hydrogenated (and fluorinated) amorphous silicon (a-Si:H(F)), within a few hours near room temperature. While the defect generation rate scales roughly with 1/G2, the saturation defect densities Ns,sat are essentially independent of G. The saturation is not due to thermal annealing. We have further measured Ns,sat m 37 a-Si:H(F) films grown in six different reactors under different conditions. The results show that Ns,sat lies between 5 × 1016 and 2 × 1017 cm−3, that Ns,sat drops with decreasing optical gap and hydrogen content, and that Ns,sat is not correlated with the initial defect density or with the Urbach energy.

scholarly journals On the Effect of Substrate Temperature on a-Si:H Deposition Using an Expanding Thermal Plasma

1996 ◽  
Vol 420 ◽  
Author(s):  
R. J. Severens ◽  
M. C. M. Van De Sanden ◽  
H. J. M. Verhoeven ◽  
J. Bastiaanssen ◽  
D. C. Schram
Keyword(s):  
Growth Rate ◽  
Substrate Temperature ◽  
Urbach Energy ◽  
Hydrogen Plasma ◽  
Hydrogen Abstraction ◽  
Plasma Jet ◽  
Hydrogenated Silicon ◽  
Amorphous Hydrogenated Silicon ◽  
Simple Kinetic Model ◽  
S Deposition

AbstractFast (7 nm/s) deposition of amorphous hydrogenated silicon with a midgap density of states less than 1016 cm-3 and an Urbach energy of 50 meV has been achieved using a remote argon/hydrogen plasma. The plasma is generated in a dc thermal arc (0.5 bar, 5 kW) and expands into a low pressure chamber (20 Pa) thus creating a plasma jet with a typical flow velocity of 103 m/s. Pure silane is injected into the jet immediately after the nozzle, in a typical flow mixture of Ar:H2:SiH4=55:10:10 scc/s. As the electron temperature in the recombining plasma is low (typ. 0.3 eV), silane radicals are thought to be produced mainly by hydrogen abstraction.Material quality in terms of refractive index, conductivity, microstructure parameter and optical bandgap was found to increase monotonously with substrate temperature, even up to 350 °C; for practically all low growth rate deposition schemes an optimum around 250 °C is observed. It will be argued that this behavior is consistent with a simple kinetic model involving physisorption and hopping, growth on dangling bonds and thermal desorption of hydrogen.

Enhanced Surface Diffusion in Low-temperature a-Si:H Processing

2004 ◽  
Vol 808 ◽  
Author(s):  
George T. Dalakos ◽  
Joel L. Plawsky ◽  
Peter D. Persans
Keyword(s):  
Surface Roughness ◽  
Surface Diffusion ◽  
Room Temperature ◽  
Cathodic Deposition ◽  
Hydrogenated Silicon ◽  
Surface Diffusivity ◽  
Amorphous Hydrogenated Silicon ◽  
Anodic Deposition ◽  
Enhanced Surface ◽  
Global Parameters

ABSTRACTGlow discharge amorphous hydrogenated silicon (a-Si:H) prepared at near room temperature typically results in an inhomogeneous morphology that is undesirable for a number of thin film applications. The most commonly observed features of this include columnar morphology and surface roughness. This usually results from anodic deposition, where substrates are placed on the grounded electrode. We have discovered that placing substrates on the RF-powered electrode (referred to as cathodic deposition) offers a much wider processing range for homogenous growth than anodic growth. We have also found that the magnitude of the surface roughness and the bulk void fraction of both anodic and cathodic a-Si:H thin films processed at low-temperatures is proportional to ∼D/F, where D is the surface diffusivity and F, the adatom flux, though anodic and cathodic deposition affect these global parameters differently. Surface processes unique to cathodic deposition can enhance adatom surface diffusion, while diffusion during anodic deposition is fixed and cannot attain homogeneous growth at high adatom fluxes. Processing a-Si:H on the cathode, associated with enhanced adatom surface diffusion, allows for homogeneous growth even at high deposition rates that has benefits for a number of applications.

Room-temperature electroluminescence of erbium-doped amorphous hydrogenated silicon

1997 ◽  
Vol 70 (2) ◽  
pp. 240-242 ◽  
Author(s):  
O. B. Gusev ◽  
A. N. Kuznetsov ◽  
E. I. Terukov ◽  
M. S. Bresler, ◽  
V. Kh. Kudoyarova ◽  
...  
Keyword(s):  
Room Temperature ◽  
Hydrogenated Silicon ◽  
Amorphous Hydrogenated Silicon ◽  
Erbium Doped

Very High-Gap Tetrahedrally Coordinated Amorphous Silicon-Carbon Alloys

1994 ◽  
Vol 336 ◽  
Author(s):  
Ionel Solomon ◽  
Leandro R. Tessler
Keyword(s):  
Amorphous Silicon ◽  
Optical Transmission ◽  
Tetrahedral Coordination ◽  
Standard Material ◽  
Urbach Tail ◽  
Silicon Carbon ◽  
Record Value ◽  
Highly Strained ◽  
Hydrogenated Amorphous ◽  
Very High

ABSTRACTWe have prepared a series of hydrogenated Amorphous silicon-carbon alloys a-Si1-xCx:H in conditions where the power delivered to the plasma is below the threshold of primary decomposition of CH4 (“low-power regime”). Carbon is therefore incorporated into the growing film in the form of methyl groups -CH3, thus preserving the sp3 hybridization in the solid. Since the carbon is deposited only by chemical reaction with the radicals produced by the decomposition of SiH4, its concentration in the alloys cannot exceed the value x=0.5.The variations of the optical gap and of the “average gap” with x, as measured by optical transmission, indicate as expected the predominantly tetrahedral coordination of the carbon, with a record value of EQ4=3.6 eV for x=0.42 (3.95 eV if corrected for the Urbach-tail absorption). Since the Si-C network does not relax to a more stable lower sp2 coordination, the material is highly strained, with an Urbach tail larger than that of the standard Material.

Bandgap Engineering of Amorphous Hydrogenated Silicon Carbide

MRS Advances ◽  
2016 ◽  
Vol 1 (43) ◽  
pp. 2929-2934 ◽  
Author(s):  
J. A. Guerra ◽  
L. M. Montañez ◽  
K. Tucto ◽  
J. Angulo ◽  
J. A. Töfflinger ◽  
...  
Keyword(s):  
Silicon Carbide ◽  
Urbach Energy ◽  
Amorphous Material ◽  
Deposition Process ◽  
Bandgap Energy ◽  
Bandgap Engineering ◽  
Hydrogenated Silicon ◽  
Hydrogen Dilution ◽  
Amorphous Hydrogenated Silicon ◽  
Proposed Model

ABSTRACTA simple model to describe the fundamental absorption of amorphous hydrogenated silicon carbide thin films based on band fluctuations is presented. It provides a general equation describing both the Urbach and Tauc regions in the absorption spectrum. In principle, our model is applicable to any amorphous material and it allows the determination of the bandgap. Here we focus on the bandgap engineering of amorphous hydrogenated silicon carbide layers. Emphasis is given on the role of hydrogen dilution during the deposition process and post deposition annealing treatments. Using the conventional Urbach and Tauc equations, it was found that an increase/decrease of the Urbach energy produces a shrink/enhancement of the Tauc-gap. On the contrary, the here proposed model provides a bandgap energy which behaves independently of the Urbach energy.

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