Dangling-Bond Relaxation and Metastability in P-Type Hydrogenated Amorphous Silicon

1995 ◽  
Vol 377 ◽  
Author(s):  
Richard S. Crandall ◽  
Martin W. Carlen ◽  
Klaus Lips ◽  
Yueqin Xu
Keyword(s):  
Elevated Temperature ◽  
Amorphous Silicon ◽  
Hydrogenated Amorphous Silicon ◽  
Type A ◽  
Dangling Bond ◽  
Dangling Bonds ◽  
Hole Trapping ◽  
P Type ◽  
Hydrogenated Amorphous

ABSTRACTWe discuss the subtle effects involved in observing slow dangling bond relaxation by studying capacitance transients in p-type hydrogenated amorphous silicon (a-Si:H). The data suggest that neutral dangling bonds are reversibly converted into metastable positive charged dangling bonds by hole trapping. These metastable positive dangling bonds reconvert to neutral dangling bonds upon annealing at elevated temperature. The annealing kinetics for this process are the same as those observed for annealing of quenched in conductivity changes in p-type a-Si:H.

Boron doping in a-SiO:H,

2014 ◽  
Vol 92 (7/8) ◽  
pp. 586-588 ◽  
Author(s):  
Y. Kitani ◽  
T. Maeda ◽  
S. Kakimoto ◽  
K. Tanaka ◽  
R. Okumoto ◽  
...  
Keyword(s):  
Amorphous Silicon ◽  
Hydrogenated Amorphous Silicon ◽  
Hole Mobility ◽  
Boron Doping ◽  
Type A ◽  
Dark Conductivity ◽  
Wide Range ◽  
P Type ◽  
Hydrogenated Amorphous ◽  
Silicon Oxygen

Boron-doping characteristics in hydrogenated amorphous silicon–oxygen alloys (a-SiO:H) have been studied in contrast to those in hydrogenated amorphous silicon (a-Si:H). Although the boron-incorporation efficiency shows almost the same value between a-SiO:H and a-Si:H, p-type a-SiO:H (p-a-SiO:H) exhibits lower dark conductivity by one or two orders of magnitude as compared to p-type a-Si:H (p-a-Si:H) in a wide range of doping levels. We have found that p-a-SiO:H exhibits low dark conductivity as compared to p-a-Si:H even when we choose samples showing the same activation energy from a variety of as-deposited and thermally annealed samples. We have concluded from the different Urbach-energy values between high quality intrinsic a-SiO:H and a-Si:H that the origin of low dark conductivity in p-a-SiO:H is due to low hole mobility.

Correlation of Film Quality and Hydrogen NMR Resonance Shifts in a-Si:D,H; a-Ge:D,H; and a-SiGe:D,H

1995 ◽  
Vol 377 ◽  
Author(s):  
R. E. Norberg ◽  
Y. W. Kim ◽  
P. H. Chan ◽  
J. R. Bodart ◽  
M. J. Kernan ◽  
...  
Keyword(s):  
Amorphous Silicon ◽  
Systematic Study ◽  
Hydrogenated Amorphous Silicon ◽  
Spectral Features ◽  
Dangling Bond ◽  
Dangling Bonds ◽  
Hydrogen Molecules ◽  
Hydrogenated Amorphous ◽  
Significant Resonance ◽  
Deposition Conditions

ABSTRACTA systematic study of both proton and deuteron NMR in hydrogenated amorphous silicon films has revealed significant resonance shifts among various resolved components. The shifts include both paramagnetic and diamagnetic displacements of resolved spectral features from trapped molecular hydrogens. The shifts depend on film quality and deposition conditions. Some of the shifts vary as 1/T and reflect Curie susceptibilities characteristic of local regions of differing dangling bond densities. Spectra from relatively immobile hydrogen molecules trapped in nanovoids are shifted diamagnetically and broadened as temperature decreases. Hydrogens tightly bound to Si do not show similar changes and thus are more remote from dangling bonds and other magnetic defects. Similar spectrally-resol ved shifts have been observed in a-Ge and a-SiGe films and are correlated with film photovoltaic quality as measured by mobility-lifetime products.

Mechanisms for Metastability in Hydrogenated Amorphous Silicon

2000 ◽  
Vol 609 ◽  
Author(s):  
R. Biswas ◽  
Y.-P. Li ◽  
B.C. Pan
Keyword(s):  
Amorphous Silicon ◽  
Structural Changes ◽  
Defect Formation ◽  
Hydrogenated Amorphous Silicon ◽  
Dangling Bond ◽  
Dangling Bonds ◽  
New Model ◽  
Gap States ◽  
Hydrogenated Amorphous ◽  
Metastable Defect

ABSTRACTWe propose metastabilities in amorphous silicon fall into two classes. One class is the local changes of structure affecting a macroscopic fraction of sites. The other class is the metastable generation of dangling bonds with mid-gap states. The local metastability is explained by a new metastable state formed when H is flipped to the backside of the Si-H bond at monohydride sites. The dipole moment of this H-flip defect is larger and increases the infrared absorption. This H-flip defect accounts for large structural changes observed on light soaking including larger absorption and volume dilation. We propose a new model for the generation of metastable dangling bonds. The new ‘silicon network rebonding model’ involves breaking of weak silicon bonds and formation of isolated dangling bonds, through rebonding of the silicon network. Hydrogen motion is not involved in metastable defect formation. Defect formation proceeds by breaking weak silicon bonds and formation of dangling bond-floating bond pairs. The floating bonds migrate through the network and annihilate, producing isolated dangling bonds. This new model provides a new platform for understanding the atomistic origins of lightinduced degradation.

Microscopic Model for Creation And Removal of Metastable Dangling Bonds in a-Si:H

2002 ◽  
Vol 715 ◽  
Author(s):  
M.J. Powell ◽  
S.C. Deane ◽  
R.B. Wehrspohn
Keyword(s):  
Amorphous Silicon ◽  
Mechanical Stress ◽  
Hydrogenated Amorphous Silicon ◽  
Microscopic Model ◽  
Stress Dependence ◽  
Dangling Bond ◽  
Dangling Bonds ◽  
Defect Creation ◽  
Hydrogenated Amorphous

AbstractWe present a new microscopic model for metastable Si dangling bond defect creation in hydrogenated amorphous silicon, which is applicable to both light-induced and carrier-induced defect creation. The key feature of our model is that hydrogen is always in the tedrahedral-like site, which is strongly bound in amorphous silicon, and never in the bond-centered site. Breaking of Si-Si bonds and successive stabilisation by bond-switching of nearby hydrogen from doubly hydrogenated Si-Si bonds (SiHHSi) results in two hydrogen-stabilised dangling bonds (SiHD). Since hydrogen is in the Td site in all configurations, this defect creation reaction is consistent with ESR, NMR, hydrogenation experiments and the mechanical stress dependence of defect creation.

Thermal Equilibrium Defects in Hydrogenated Amorphous Silicon Based Alloy Films

1989 ◽  
Vol 149 ◽  
Author(s):  
Xixiang Xu ◽  
Akiharu Morimoto ◽  
Minoru Kumeda ◽  
Tatsuo Shimizu
Keyword(s):  
Elevated Temperature ◽  
Amorphous Silicon ◽  
Thermal Equilibrium ◽  
Hydrogenated Amorphous Silicon ◽  
Dangling Bonds ◽  
Alloy Films ◽  
Fast Cooling ◽  
Silicon Based ◽  
Equilibrium Defects ◽  
Hydrogenated Amorphous

ABSTRACTBoth the temperature dependence at elevated temperature and the increase after fast cooling from elevated temperature of the density of dangling bonds are measured by ESR for undoped hydrogenated amorphous silicon–based alloy films, a–Si:H, a–Si1−xCx:H, a–Si1−xNx:H and a–Si1−xOx:H. Both a–Si:H and a–Si1−xCx:H clearly show the increase in the density of dangling bonds at elevated temperature, while the increase is less prominent for a–Si1−xNx:H and a–Si1−xOx:H. The observed results for both a–Si:H and a–Si1−xCx:H are fairly well reproduced by the model recently proposed by Smith et al. The results of CPM measurements combined with those of ESR measurements suggest that the density of charged dangling bonds present in undoped a–Si:H also increases after fast cooling from elevated temperature.

Doping Mechanism in Tetrahedral Amorphous Carbon

1997 ◽  
Vol 498 ◽  
Author(s):  
C W Chen ◽  
J Robertson
Keyword(s):  
Amorphous Silicon ◽  
Amorphous Carbon ◽  
Hydrogenated Amorphous Silicon ◽  
Donor Atom ◽  
Dangling Bond ◽  
Coulombic Repulsion ◽  
Tetrahedral Amorphous Carbon ◽  
Total Energies ◽  
Doping Mechanism ◽  
Hydrogenated Amorphous

ABSTRACTDoping in hydrogenated amorphous silicon occurs by a process of an ionised donor atom partially compensated by a charged dangling bond. The total energies of various dopant and dopant/bonding combinations are calculated for tetrahedral amorphous carbon. It is found that charged dangling bonds are less favoured because of the stronger Coulombic repulsion in ta-C. Instead the dopants can be compensated by weak bond states in the lower gap associated with odd-membered π-rings or odd-numbered π-chains. The effect is that the doping efficiency is low but there are not charged midgap recombination centres, to reduce photoconductivity or photoluminescence with doping, as occurs in a-Si:H.

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