Improved defect-pool model for charged defects in amorphous silicon

1993 ◽  
Vol 48 (15) ◽  
pp. 10815-10827 ◽  
Author(s):  
M. J. Powell ◽  
S. C. Deane
Keyword(s):  
Amorphous Silicon ◽  
Pool Model ◽  
Charged Defects

The Role of Charged Defects In Current Transport Through Hydrogenated Amorphous Silicon Alloys

1998 ◽  
Vol 507 ◽  
Author(s):  
S.P. Lau ◽  
J.M. Shannon ◽  
B.J. Sealy ◽  
J.M. Marshall
Keyword(s):  
Silicon Nitride ◽  
Amorphous Silicon ◽  
Defect Density ◽  
Current Transport ◽  
Dangling Bond ◽  
Silicon Alloys ◽  
Metal Structures ◽  
Bond State ◽  
Donor States ◽  
Charged Defects

ABSTRACTCurrent transport in metal-semiconductor-metal structures based on amorphous silicon alloys has been studied in relation to the density of dangling bond state defects. The density of defects was changed by varying alloy composition or by current stressing. We show that the change of current-voltage characteristics and activation energy with defect density and the onset of Poole-Frenkel conduction with composition require charged defects. It is found that there are more charged defects in amorphous silicon nitride (a-Si1−xNx:H) than in amorphous silicon carbide (a-Si1−xCx:H). In addition, an excess of negatively charged dangling bond defects compared to positively charged dangling bond defects is observed in a-Si1−xNx:H films. This is attributed to the presence of N4+ act as the donor states in silicon nitride. We find that the density of charged dangling bond defects can be higher than 1019cm−3.

Experimental evidence of boron induced charged defects in amorphous silicon materials

1999 ◽  
Vol 348 (1-2) ◽  
pp. 79-83 ◽  
Author(s):  
D Caputo ◽  
G de Cesare ◽  
A Nascetti ◽  
F Palma
Keyword(s):  
Experimental Evidence ◽  
Amorphous Silicon ◽  
Silicon Materials ◽  
Charged Defects

Identification of the Dominant Electron Deep Trap in a-Si:H: A Critical Test of the Defect Pool vs. Defect Relaxation Pictures

1997 ◽  
Vol 467 ◽  
Author(s):  
Daewon Kwon ◽  
J. David Cohen
Keyword(s):  
Fermi Level ◽  
Thermal Emission ◽  
Deep Trap ◽  
Esr Spectra ◽  
Defect Band ◽  
Large Populations ◽  
Pool Model ◽  
Charged Defects ◽  
Defect Relaxation ◽  
Rule Out

ABSTRACTModulated photocurrent (MPC) measurements in intrinsic a-Si:H reveal a prominent band of electron deep traps with a thermal emission energy near 0.6eV. We have identified this defect band by directly comparing MPC and ESR spectra for both an intrinsic and a lightly n-type doped sample for a various metastable states such that the Fermi level, EF, ranges from less than 0.5eV to more than 0.7eV below Ec. This comparsion unambiguously demonstrates that the MPC band arises from the Do charge state of the defects (specifically, the D−&Do transition). This identification is also confirmed when the quasi-Fermi level is varied by the application of light bias even though the peak emission rate from the MPC defect band is changed by more than a factor of 100. These observations specifically rule out the possibility of large populations of charged defects in intrinsic samples predicted by proponents of the defect pool model. Instead, observed behaviors have a natural explanation in terms of a defect relaxation process.

LONG-RANGE FLUCTUATIONS OF RANDOM POTENTIAL LANDSCAPE AS A MECHANISM OF 1/f NOISE IN HYDROGENATED AMORPHOUS SILICON

2005 ◽  
Vol 05 (03) ◽  
pp. L443-L456
Author(s):  
BORIS V. FINE ◽  
JEROEN P. R. BAKKER ◽  
JAAP I. DIJKHUIS
Keyword(s):  
Amorphous Silicon ◽  
Long Range ◽  
Noise Intensity ◽  
Broad Class ◽  
Hydrogenated Amorphous Silicon ◽  
Low Frequency ◽  
Noise Spectrum ◽  
Current Flows ◽  
Charged Defects ◽  
Hydrogenated Amorphous

We describe a mechanism that links the long-range potential fluctuations induced by charged defects to the low-frequency resistance noise widely known as 1/fnoise. This mechanism is amenable to the first principles microscopic calculation of the noise spectrum, which includes the absolute noise intensity. We have performed such a calculation for the thin films of hydrogenated amorphous silicon ( a-Si:H ) under the condition that current flows perpendicular to the plane of the films, and have found a very good agreement between the theoretical noise intensity and the measured one. The mechanism described is quite general. It should be present in a broad class of systems containing poorly screened charged defects.

A Unified Description of the Density of States for Hydrogen and Electrons in Amorphous Silicon

1994 ◽  
Vol 336 ◽  
Author(s):  
S.C. Deane ◽  
M.J. Powell
Keyword(s):  
Amorphous Silicon ◽  
Density Of States ◽  
Correlation Energy ◽  
Dangling Bond ◽  
Hydrogen Binding ◽  
Electronic Density ◽  
Hydrogen Density ◽  
Electronic Density Of States ◽  
Defect Sites ◽  
Pool Model

ABSTRACTWe derive the hydrogen density of states for hydrogenated Amorphous silicon (a-Si:H), which is completely consistent with the electronic density of states for the defect pool model. If silicon dangling bond energies are distributed in energy, as in a defect pool model, then the hydrogen density of states becomes quite complex, with the hydrogen binding energy dependent on the Fermi level and dangling bond transition energy. We demonstrate that the electronic density of states for dangling bonds is almost identical to our previous defect pool model, while the hydrogen density of states can account for the results of hydrogenation-dehydrogenation experiments. The effective hydrogen correlation energy is variable, being negative for most hydrogen binding sites, but positive for most defect sites.

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