The Photoconductivity Exponent For Recombination At Dangling Bonds In a-Si:H

1986 ◽  
Vol 70 ◽  
Author(s):  
F. Vaillant ◽  
D. Jousse
Keyword(s):  
Cross Section ◽  
Capture Cross Section ◽  
Correlation Energy ◽  
Detailed Balance ◽  
Parametric Representation ◽  
Capture Cross ◽  
Dangling Bond ◽  
Dangling Bonds ◽  
Bond Density ◽  
Good Agreement

ABSTRACTA theoretical model has been developed for recombination at dangling bonds which explains the γ variations between 0.5 and 1 depending on the Fermi level position. The occupation probabilities of the T3+, T3° and T3- states under illumination have been calculated using the statistics of correlated levels. The γ exponent is derived through a parametric representation of the equations of detailed balance and charge conservation. A good agreement with experiment is obtained with a dangling bond density of 5×1015 cm-3, a placing of the T3° level at 0.95 eV below Ec, an effective correlation energy of 0.4 eV and a charged to neutral capture cross section ratio of 50.

Interface States in 4H- and 6H-SiC MOS Capacitors: A Comparative Study between Conductance Spectroscopy and Thermal Dielectric Relaxation Current Technique

2009 ◽  
Vol 615-617 ◽  
pp. 497-500 ◽  
Author(s):  
Lars S. Løvlie ◽  
Ioana Pintilie ◽  
S. Kumar C.P. ◽  
Ulrike Grossner ◽  
Bengt Gunnar Svensson ◽  
...  
Keyword(s):  
Comparative Study ◽  
Dielectric Relaxation ◽  
Cross Section ◽  
Capture Cross Section ◽  
Interface States ◽  
Conduction Band Edge ◽  
Capture Cross ◽  
Mos Capacitors ◽  
Dry Oxidation ◽  
Good Agreement

The purpose of this work is to compare the density of shallow interface states (Dit) at the interface of SiO2/SiC MOS capacitors as deducted by the conductance spectroscopy (CS) and thermally dielectric relaxation current (TDRC) techniques. Both capacitors of 4H- and 6H-SiC (n-type) are investigated, and both ordinary dry oxidation and an improved industrial procedure have been employed. The two techniques are found to give rather good agreement for interface states located ≥0.3 eV below the conduction band edge (Ec) while for more shallow states vastly different distributions of Dit are obtained. Different reasons for these contradictory results are discussed, such as strong temperature and energy dependence of the capture cross section of the shallow interface states.

AC Theory of Constant Photocurrent Measurement

1995 ◽  
Vol 377 ◽  
Author(s):  
G. Conte ◽  
A. Eray ◽  
G. Nobile ◽  
F. Palma
Keyword(s):  
Cross Section ◽  
Capture Cross Section ◽  
Small Signal ◽  
Capture Cross ◽  
Charge Accumulation ◽  
Test Frequency ◽  
Dangling Bond ◽  
Large Phase ◽  
Photocurrent Measurement ◽  
Method Of Evaluation

ABSTRACTIn this paper we present a study of ac the Constant Photocurrent Measurement (CPM) with the aim to assess the precision of this method compared to the de CPM. In particular, we introduce a small signal theory of the ac photoconductivity, we relate the sub-bandgap absorption to the density of defects, and we assume a combination of a constant plus a sinusoidal generation rate. The method allows to calculate the variation occurring in defect occupation as a function of the wavelength and intensity of the light, and of the ac test frequency. We show that, in ac condition, carriers lifetime is a complicated function of the chosen parameter, and it is affected by the delay due to charge accumulation of free and trapped carrier densities. Large influence on the lifetime is played not only by recombination, which takes place all along the gap defects included between the two quasi-Fermi levels, but also by the process of carrier trapping and emission by defects located close to the quasi-Fermi levels. Both processes introduce large phase delay. Further information can thus be obtained from CPM by evaluating the phase behavior. Our analysis leads to a new method of evaluation of the dangling bond capture cross section and of their charged-to-neutral capture cross section ratio.

Charged Dangling Bonds and Crystallization in Group IV Semiconductors

1982 ◽  
Vol 13 ◽  
Author(s):  
P.J. Germain ◽  
M.A. Paesler ◽  
D.E. Sayers ◽  
K. Zellama
Keyword(s):  
Activation Energy ◽  
Growth Rate ◽  
Ionizing Radiation ◽  
Cross Section ◽  
Capture Cross Section ◽  
Group Iv ◽  
Capture Cross ◽  
Dangling Bonds ◽  
Group Iv Semiconductors ◽  
Increasing Function

ABSTRACTCrystallization of amorphous Ge (or Si) has been studied as a function of temperature and the flux of ionizing radiation (or doping). The crystallization growth rate Vg takes on the form Vg = vo exp(−E/kT) where vo is an increasing function of flux (or doping). We propose the following to explain these data: A concentration of mobile dangling bonds (DBs) exists in the bulk and near the amorphous-crystalline (a-c) interface. Ionization and doping induce transitions from the uncharged state Do to the charged states D+ and D−. The process controlling crystallization resulting in the above activation energy is discussed. Only certain sites on the a-side of the a-c interface are available for crystallization, and these sites are those which have captured DBs. The charged D+; and D− states have a larger capture cross section than the uncharged Do state. Increased concentrations of charged DBs results in an enhancement of the prefactor in the above equation.

On Modeling Trivalent Dangling Bonds with Bivalent Levels

1994 ◽  
Vol 336 ◽  
Author(s):  
Vyshnavi Suntharalingam ◽  
Howard M. Branz
Keyword(s):  
Charge Density ◽  
Cross Section ◽  
Recombination Rate ◽  
Thermal Equilibrium ◽  
Capture Cross Section ◽  
Hydrogenated Amorphous Silicon ◽  
Capture Cross ◽  
Dangling Bond ◽  
Band Bending ◽  
Hydrogenated Amorphous

ABSTRACTWe examine the treatment of the hydrogenated Amorphous silicon (a-Si:H) dangling-bond defect used in the Analysis of microelectronic and Photonic Structures (AMPS) computer model and in other models of a-Si:H semiconductor devices. The dangling bond defect (D) is trivalent, with two correlated electronic levels in the gap. However, Modelers typically employ two uncorrelated bivalent levels to represent D; this introduces fictitious neutral dangling bond (D°) levels whenever D is charged. We find that the bivalent (AMPS) representation captures the important aspects of D physics and introduces only small errors into simulations. To reach this conclusion, we examine charge density and recombination and compare the trivalent D defect and its bivalent representation in both thermal equilibrium and non-equilibrium (illuminated) cases. The charge density is identical, implying that band bending computed by the simulation is accurate. We find errors in the recombination rate for the bivalent representation are normally less than or equal to σ0/σch, where σ° is the capture cross section of D0 and σch is the capture cross section of a charged state of D. Typically Modelers use σ0/σch of 1:10 to 1:100 yielding insignificant errors in the recombination rate with the uncorrelated bivalent representation.

Thermal Quenching and Photo-Enhancement of μτ Products in a-Si:H - The Role of Dangling Bonds and Band Tails

1994 ◽  
Vol 336 ◽  
Author(s):  
E. Morgado
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Capture Cross Section ◽  
Thermal Quenching ◽  
Capture Cross ◽  
Dangling Bond ◽  
Temperature Dependences ◽  
Capture Cross Sections ◽  
Band Tails

ABSTRACTResults from numerical calculations with a recombination model involving one class of correlated dangling-bond states and exponential band tails, in a-Si:H, are reported. Fermi level, light intensity and temperature dependences of the μτ products are studied. The results are consistent with experimental data. It is found that photo-enhancement of (μτ)e, or superlinear photoconductivity, as well as thermal quenching, are associated with a capture cross section of the band tails smaller than the capture cross sections of the dangling-bond states.

Measurements of the neutron capture cross section of 243Am around 23.5 keV

2021 ◽  
pp. 1-6
Author(s):  
Yu Kodama ◽  
Tatsuya Katabuchi ◽  
Gerard Rovira ◽  
Atsushi Kimura ◽  
Shoji Nakamura ◽  
...  
Keyword(s):  
Cross Section ◽  
Neutron Capture ◽  
Capture Cross Section ◽  
Capture Cross ◽  
Neutron Capture Cross Section
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