Capacitance and Transient Photocapacitance Studies of Tetrahedral Amorphous Carbon

2000 ◽  
Vol 621 ◽  
Author(s):  
Kimon C. Palinginis ◽  
A. Ilie ◽  
W.I. Milne ◽  
J. David Cohen
Keyword(s):  
Amorphous Carbon ◽  
Urbach Energy ◽  
Defect Density ◽  
Intrinsic Property ◽  
Band Tail ◽  
Junction Capacitance ◽  
Tetrahedral Amorphous Carbon ◽  
Thermally Activated ◽  
A Value ◽  
Defect Densities

ABSTRACTWe have applied junction capacitance and transient photocapacitance measurements to undoped tetrahedral amorphous carbon (ta-C)/silicon carbide (SiC) heterostructures to deduce defect densities and defect distributions in ta-C. The junction capacitance measurements show two thermally activated processes. One can be related to the activation of carriers out of defects at the ta-C/SiC interface while the other one with an activation energy of 0.36eV is an intrinsic property of the ta-C. The defect density at the ta-C/SiC interface is estimated to be roughly 9 ± 2 × 109 cm−2. The transient photocapacitance measurements have allowed us to observe the broader band tail of ta-C, giving a value (Urbach energy) of 230meV.

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.

Characterization of Tetrahedrally Bonded Amorphous Carbon Via Capacitance Techniques

1998 ◽  
Vol 508 ◽  
Author(s):  
Kimon C. Palinginis ◽  
A. Ilie ◽  
B. Kleinsorge ◽  
W.I. Milne ◽  
J. D. Cohen
Keyword(s):  
Amorphous Carbon ◽  
Thermal Activation ◽  
Activation Process ◽  
Defect States ◽  
Capacitance Measurements ◽  
Tetrahedral Amorphous Carbon ◽  
Thermal Activation Process ◽  
Order Of Magnitude ◽  
Defect Densities

AbstractWe report the results of junction capacitance measurements on thin tetrahedral amorphous carbon (ta-C) films to deduce their defect densities. We find defect densities in the range 3 - 7 × 1017 cm−3 in the undoped ta-C films, and roughly an order of magnitude larger in the nitrogen doped (n-type) films. In some cases fairly uniform defect profiles were obtained covering a thickness of a couple of hundreds angstroems. We also observed a thermal activation process of carriers from defect states at the ta-C/c-Si interface with an activation energy in the range of 0.4eV to 0.5eV.

Defect densities in tetrahedrally bonded amorphous carbon deduced by junction capacitance techniques

1999 ◽  
Vol 74 (3) ◽  
pp. 371-373 ◽  
Author(s):  
Kimon C. Palinginis ◽  
Yoram Lubianiker ◽  
J. David Cohen ◽  
Adelina Ilie ◽  
Britta Kleinsorge ◽  
...  
Keyword(s):  
Amorphous Carbon ◽  
Junction Capacitance ◽  
Defect Densities ◽  
Tetrahedrally Bonded

Effect of Light Soaking on Hot Wire Deposited a-Si:H Films

1995 ◽  
Vol 377 ◽  
Author(s):  
Daewon Kwon ◽  
J. David Cohen ◽  
Brent P. Nelson ◽  
Eugene Iwaniczko
Keyword(s):  
Physical Properties ◽  
Hydrogen Content ◽  
Defect Density ◽  
Hot Wire ◽  
Junction Capacitance ◽  
Capacitance Measurements ◽  
Hydrogen Level ◽  
Defect Densities ◽  
Effect Of Light ◽  
Good Agreement

ABSTRACTWe present the results of studies on the defect properties and the effect of light soaking for various hot wire deposited (HW) films. We employ junction capacitance measurements together with the transient photocapacitance spectroscopy to measure the deep defect densities in as-grown state (state A) and in light soaked state (state B). Good agreement is found between the defect densities measured from both measurements. The HW film with a hydrogen content of 10 – 12 at.% shows physical characteristics and defect densities similar to conventional PECVD films. The HW films with hydrogen content, CH, in the range 2 – 9 at.% show a smaller defect density in state B than the defect density of the film with higher CH. However, the film with a hydrogen level of less than 1 at.% exhibits markedly inferior physical properties.

Reduction in defect density by annealing in hydrogenated tetrahedral amorphous carbon

1998 ◽  
Vol 73 (17) ◽  
pp. 2456-2458 ◽  
Author(s):  
N. M. J. Conway ◽  
A. Ilie ◽  
J. Robertson ◽  
W. I. Milne ◽  
A. Tagliaferro
Keyword(s):  
Amorphous Carbon ◽  
Defect Density ◽  
Tetrahedral Amorphous Carbon

Isolation of Temperature Effects on the Kinetics of Light Induced Defect Generation in a-Si:H

1992 ◽  
Vol 258 ◽  
Author(s):  
L. Benatar ◽  
M. Grimbergen ◽  
A. Fahrenbruch ◽  
A. Lopez-Otero ◽  
D. Redfield ◽  
...  
Keyword(s):  
Defect Formation ◽  
Defect Density ◽  
Dark Conductivity ◽  
Stretched Exponential ◽  
Defect Generation ◽  
Thermally Activated ◽  
A Value ◽  
Effects Of Temperature ◽  
Kinetics Of

ABSTRACTData are presented here that show the effects of temperature on the kinetics of metastable defect formation in undoped a-Si:H over the range 45°-110°C. CPM (Constant Photocurrent Method), photoconductivity, and dark conductivity measurements were made and provide independent checks of the defect generation behavior. A stretched exponential description of defect formation as a function of time was used to fit the CPM defect density data. The stretched exponential time constant, τSE, is thermally activated with an apparent activation energy of 1 eV, a value that agrees well with data for defect anneal and solar cell degradation. The data indicate that thermal terms are not negligible for temperatures as low as 45°C, and therefore should be included in any model of the kinetics of defect formation. The role of adistribution of anneal energies and the regimes of dominance of thermal and optical rate terms are discussed in the context of the model.

Material Properties of a-SiGe:H Solar Cells as a Function of Growth Rate

2010 ◽  
Vol 1245 ◽  
Author(s):  
Peter Hugger ◽  
JinWoo Lee ◽  
J. David Cohen ◽  
Guozhen Yue ◽  
Xixiang Xu ◽  
...  
Keyword(s):  
Valence Band ◽  
Material Properties ◽  
Defect Density ◽  
Schottky Contact ◽  
Drive Level ◽  
Measurement Methods ◽  
Device Performance ◽  
Band Tail ◽  
Contact Devices ◽  
Defect Densities

AbstractWe have examined a series of a Si,Ge:H alloy devices deposited using both RF and VHF glow discharge in two configurations: SS/n+/i (a-SiGe:H)/p+/ITO nip devices and SS/n+/i (a-SiGe:H)/Pd Schottky contact devices, over a range of deposition rates. We employed drive-level capacitance profiling (DLCP), modulated photocurrent (MPC), and transient junction photo-current (TPI) measurement methods to characterize the electronic properties in these materials. The DLCP profiles indicated quite low defect densities (mid 1015 cm-3. to low 1016 cm-3 depending on the Ge alloy fraction) for the low rate RF (∼1Å/s) deposited a-SiGe:H materials. In contrast to the RF process, the VHF deposited a-SiGe:H materials did not exhibit nearly as rapid an increase of defect density with the deposition rate, remaining well below 1017 cm-3. up to rates as high as 10Å/s. Simple examination of the TPI spectra on theses devices allowed us to determine valence band-tail widths.. Modulated photocurrent (MPC) obtained for several of these a-SiGe:H devices allowed us to deduce the conduction band-tail widths. In general, the a-Si,Ge:H materials exhibiting narrower valence band-tail widths and lower defect densities correlated with the best device performance.

Defect density and atomic bond structure of tetrahedral amorphous carbon (ta-C) films prepared by filtered vacuum arc process

2004 ◽  
Vol 95 (9) ◽  
pp. 4829-4832 ◽  
Author(s):  
Churl Seung Lee ◽  
Jin-Koog Shin ◽  
Kwang Yong Eun ◽  
Kwang-Ryeol Lee ◽  
Ki Hyun Yoon
Keyword(s):  
Amorphous Carbon ◽  
Defect Density ◽  
Vacuum Arc ◽  
Tetrahedral Amorphous Carbon

Characterization of Tetrahedrally Bonded Amorphous Carbon Via Capacitance Techniques

1998 ◽  
Vol 509 ◽  
Author(s):  
Kimon C. Palinginis ◽  
A. Ilie ◽  
B. Kleinsorge ◽  
W.I. Milne ◽  
J. D. Cohen
Keyword(s):  
Amorphous Carbon ◽  
Thermal Activation ◽  
Activation Process ◽  
Defect States ◽  
Capacitance Measurements ◽  
Tetrahedral Amorphous Carbon ◽  
Thermal Activation Process ◽  
Order Of Magnitude ◽  
Defect Densities

AbstractWe report the results of junction capacitance measurements on thin tetrahedral amorphous carbon (ta-C) films to deduce their defect densities. We find defect densities in the range 3 - 7 × 1017 cm−3 in the undoped ta-C films, and roughly an order of magnitude larger in the nitrogen doped (n-type) films. In some cases fairly uniform defect profiles were obtained covering a thickness of a couple of hundreds angstroems. We also observed a thermal activation process of carriers from defect states at the ta-C/c-Si interface with an activation energy in the range of 0.4eV to 0.5eV.

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