Electronic Transport Properties of a-Si:H,F/a-Si,Ge:H,F Superlattices

1987 ◽  
Vol 95 ◽  
Author(s):  
J. P. Conde ◽  
S. Aljishi ◽  
D. S. Shen ◽  
V. Chu ◽  
Z E. Smith ◽  
...  
Keyword(s):  
Barrier Layer ◽  
Electronic Transport ◽  
Thermal Emission ◽  
Parallel Transport ◽  
Dark Conductivity ◽  
Alloy Layer ◽  
Conductivity Activation Energy ◽  
Superlattice Structures ◽  
Deposition Conditions ◽  
Extract Information

AbstractWe study the dark conductivity σd, dark conductivity activation energy Ea and photoconductivity σph of a-Si:H,F/a-Si,Ge:H,F superlattices both perpendicular and parallel to the plane of the layers. In parallel transport, both the σph and σd are dominated by the alloy layer characteristics with the superposition of carrier confinement quantum effects. In perpendicular transport, the σd shows an interplay of quantum mechanical tunneling through the barriers and of classical thermal emission over the barrier layer and the σph is controlled by the decreasing absorption by the silicon barrier layer as the optical gap Eopt of the structure decreases.We also found that the multilayer structure allows to grow lower gap a-Si,Ge:H,F alloys than achievable under the same deposition conditions for bulk materials. This stabilizing effect allowed us to study low-gap superlattice structures and extract information about these very low gap (<1.2 eV) a- Si,Ge:H,F alloys.

Recombination and Electronic Transport in Low-Gap a-Si,Ge:H,F Alloys

1987 ◽  
Vol 95 ◽  
Author(s):  
S. Aljishi ◽  
D. S. Shen ◽  
V. Chu ◽  
Z E. Smith ◽  
J. P. Conde ◽  
...  
Keyword(s):  
Conduction Band ◽  
Electronic Transport ◽  
Room Temperature ◽  
Dark Conductivity ◽  
Electron Trapping ◽  
Conduction Band Edge ◽  
Band Tail ◽  
Intensity Dependence ◽  
Defect Densities ◽  
Deposition Conditions

AbstractWe have studied the temperature and intensity dependence (130K to 300K) of photo- and dark conductivity in a series of low-gap a-Si,Ge:H,F alloys (Eopt=1.25 to 1.33 eV) prepared under different deposition conditions. Electron time of flight experiments were conducted between 300K and 400K. Results reveal an increase in the slope of the exponential conduction band tail to ∼ 50 meV and a peak in electron trapping states at 0.3 to 0.4 eV below the conduction band edge, leading to a transition from extended to hopping conduction by electrons at slightly below room temperature. The alloys have midgap defect densities in the low 1017 cm−3eV−1 range.

Simultaneous Relaxation of Network and Defects in Silicon-Implanted a-Si:H

1995 ◽  
Vol 377 ◽  
Author(s):  
J. Nakata ◽  
S. Sherman ◽  
S. Wagner ◽  
P. A. Stolk ◽  
J. M. Poate
Keyword(s):  
Electronic Transport ◽  
Annealing Temperature ◽  
Urbach Energy ◽  
Defect Density ◽  
Dark Conductivity ◽  
Equilibrium Theory ◽  
Hopping Conduction ◽  
Dangling Bond ◽  
Bond Density ◽  
Additional Illumination

ABSTRACTWe report extensive optical and electronic transport data on silicon-implanted a-Si:H, annealed in steps in the dark or with additional illumination. All measured properties relax gradually with increasing annealing temperature. The dark conductivity of the as-implanted film is dominated by hopping conduction via midgap defects. This channel is pinched off during the initial stages of annealing. The midgap defect density and the Urbach energy follow an annealing path that agrees qualitatively with the trajectory postulated by the equilibrium theory of the dangling-bond density. Therefore, the silicon network and the defect density equilibrate continuously during network relaxation.

Elastic-relaxation-induced barrier layer thickness undulations in InP/GaAs type-II quantum well superlattice structures

2012 ◽  
Vol 27 (10) ◽  
pp. 105031 ◽  
Author(s):  
S D Singh ◽  
Ravi Kumar ◽  
C Mukherjee ◽  
Pushpen Mondal ◽  
A K Srivastava ◽  
...  
Keyword(s):  
Quantum Well ◽  
Layer Thickness ◽  
Barrier Layer ◽  
Type Ii ◽  
Barrier Layer Thickness ◽  
Superlattice Structures

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.

A Low Temperature Plasma-Assisted Deposition Process for Microcrystalline Thin Film Transistors, TFTS

1994 ◽  
Vol 336 ◽  
Author(s):  
S.S. He ◽  
G. Lucovsky
Keyword(s):  
Low Temperature ◽  
Deposition Process ◽  
Dark Conductivity ◽  
Low Temperature Plasma ◽  
Conductivity Activation Energy ◽  
Temperature Plasma ◽  
Threshold Voltages ◽  
Gate Structure ◽  
Saturation Region ◽  
Effective Channel

ABSTRACTThe drive-current of low-temperature (∼300°C) deposited TFTs has been increased by replacing the a-Si:H channel, and source and drain materials with μc-Si. Lightly B2H6 doped, near-intrinsic μc-Si has been used as the channel layer of the TFTs, and n+ μc-Si was used for the source and drain contacts. The compensation of intrinsic defects in the undoped μc-Si by boron doping increases the dark conductivity activation energy from -0.35 eV to 0.8 eV. TFTs were fabricated in a bottom gate structure, and required an H2 plasma treatment to produce devices with effective channel mobilities of -6.8 cm2/V-s and threshold voltages of -3.7 V in the saturation region.

Electronic transport and structure of microcrystalline silicon deposited by the VHF-GD technique

1997 ◽  
Vol 467 ◽  
Author(s):  
M. Goerlitzer ◽  
N. Beck ◽  
P. Torres ◽  
U. Kroll ◽  
H. Keppner ◽  
...  
Keyword(s):  
Transport Properties ◽  
Electronic Transport ◽  
Growth Direction ◽  
Dark Conductivity ◽  
Drift Mobility ◽  
X Ray Diffraction ◽  
Microcrystalline Silicon ◽  
Direction Parallel ◽  
X Ray ◽  
Diffraction Patterns

ABSTRACTElectronic transport parallel and perpendicular to growth direction has been studied in a series of microcrystalline silicon samples obtained by various dilutions of silane in hydrogen. It is clearly shown that the transport properties (dark conductivity, drift mobility, ambipolar diffusion length and photoconductivity) under dark and under illumination conditions are enhanced as the dilution is increased. Furthermore, these films exhibit no degradation upon light-soaking. X-Ray diffraction patterns of the samples confirm that there is a correlation between the amount of crystalline fraction in the samples and the transport properties, as well as a preferential orientation along the growth direction. A similar correlation is found with the shift of the Si-H stretching mode peak of the infrared spectra (IR). Because transport properties have been measured by different techniques (dark conductivity, ambipolar length and photoconductivity in the direction perpendicular to growth direction, drift mobility in the direction parallel to growth direction), no statement can be made about a possible anisotropy in transport, as it would be expected from the columnar shape of the crystallites.

Synthesis and characterization of single-crystal indium nitride nanowires

2004 ◽  
Vol 19 (2) ◽  
pp. 423-426 ◽  
Author(s):  
Tao Tang ◽  
Song Han ◽  
Wu Jin ◽  
Xiaolei Liu ◽  
Chao Li ◽  
...  
Keyword(s):  
Electronic Transport ◽  
Room Temperature ◽  
Thermal Emission ◽  
Indium Nitride ◽  
Chemical Vapor ◽  
Gold Clusters ◽  
Vapor Generation ◽  
Vapor Deposition Technique ◽  
Single Nanowires

InN nanowires were synthesized and characterized using a variety of techniques. A two-zone chemical vapor deposition technique was used to operate the vapor generation and the nanowire growth at differential temperatures, leading to high-quality single-crystalline nanowires and growth rates as high as 4–10 μm/h. Precise diameter control was achieved by using monodispersed gold clusters as the catalyst. Photoluminescence and Raman studies have been carried out for the InN nanowires at room temperature. Devices consisting of single nanowires have been fabricated to explore their electronic transport properties. The temperature dependence of the conductance revealed thermal emission as the dominating transport mechanism.

Ambipolar Phototransport (μτe = μτh) Observed as an Intrinsic Property of a-SiGe:H

1997 ◽  
Vol 467 ◽  
Author(s):  
Paul Wickboldt ◽  
Dawen Pang ◽  
William Paul ◽  
Joseph H. Chen ◽  
Chih-Chiang Chen ◽  
...  
Keyword(s):  
Gas Phase ◽  
Diffusion Length ◽  
Dopant Concentration ◽  
Intrinsic Property ◽  
Dark Conductivity ◽  
Air Leak ◽  
Cathodic Deposition ◽  
Conductivity Activation Energy ◽  
Unusual Behavior ◽  
Film Properties

ABSTRACTA study is presented of a series of high quality PECVD a-Si0.33Ge0.67 films, produced by cathodic deposition, in which small concentrations of PH3, B2H6 or air impurities were added during deposition. The quantum efficiency-mobility-lifetime product (ημτ) increases, and the ambipolar diffusion length (Lamb) decreases monotonically with dopant concentration for both PH3 and B2H6. This result is strong evidence that for these films neither photocarrier is dominant (μτe= μτh) at zero doping. This result is very different from what has been typically observed by other researchers, that the electron is the dominant photocarrier for undoped a-SiGe:H.Drive level capacitance (DLC) measurements of these alloys show an unusual behavior of being temperature-independent, and the dark conductivity activation energy is maximum for zero doping. It is proposed that all of these unusual properties are due to the unusually low impurity concentration of these films, and that these properties are, in fact, the intrinsic properties for a-SiGe:H alloys. To verify this, films were prepared with a calibrated and controlled air leak introduced during deposition. As the air leak was increased, the film properties changed to typical behavior. Even for air concentrations as low as 2 ppm (gas phase), the transport measurements showed changes consistent with a shift in the Fermi level toward the conduction band.

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.

Hydrogenated Amorphous Silicon Thin Films with Nanocrystalline Silicon Inclusions

2003 ◽  
Vol 762 ◽  
Author(s):  
T. J. Belich ◽  
S. Thompson ◽  
C.R. Perrey ◽  
U. Kortshagen ◽  
C.B. Carter ◽  
...  
Keyword(s):  
Thin Films ◽  
Amorphous Silicon ◽  
Hydrogenated Amorphous Silicon ◽  
Nanocrystalline Silicon ◽  
Dark Conductivity ◽  
Capacitively Coupled ◽  
Silicon Thin Films ◽  
High Resolution Tem ◽  
Hydrogenated Amorphous ◽  
Deposition Conditions

AbstractThin films of hydrogenated amorphous silicon containing nanocrystalline silicon inclusions (a/nc-Si:H) have been synthesized in an RF capacitively coupled PECVD system using a mixture of hydrogen diluted silane and helium, under deposition conditions at the edge of powder formation within the plasma. High resolution TEM confirms the presence of nanocrystallites as small as 2 nm in these films. Measurements of the optical absorption spectrum using CPM and PDS indicates a broadening of the Urbach slope in the a/nc-Si:H, compared to a-Si:H films, but no appreciable increase in midgap absorption. Despite the deposition conditions for the a/nc-Si:H being very different from those associated with producing optimal quality a-Si:H, the dark conductivity and photoconductivity values, and the sensitivity to light-induced defect creation in the a/nc-Si:H films are comparable to those in a-Si:H.

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