Influence of relaxation processes on the evaluation of the metastable defect density in Cu(In,Ga)Se2

2016 ◽  
Vol 119 (21) ◽  
pp. 215103 ◽  
Author(s):  
M. Maciaszek ◽  
P. Zabierowski
Keyword(s):  
Defect Density ◽  
Relaxation Processes ◽  
Metastable Defect

Light-Induced Metastable Defects or Light-Induced Metastable H Atoms in a-Si:H Films?

1997 ◽  
Vol 467 ◽  
Author(s):  
C. Godet
Keyword(s):  
Experimental Data ◽  
Characteristic Time ◽  
Defect Density ◽  
Hydrogenated Amorphous Silicon ◽  
Exponential Time ◽  
Mobile Species ◽  
Hydrogenated Amorphous ◽  
Two Parameter ◽  
Metastable Defect ◽  
Trapping Sites

ABSTRACTIn hydrogenated amorphous silicon (a-Si:H) films, the increase of the metastable defect density under high-intensity illumination is usually described by an empirical two-parameter stretched-exponential time dependence (characteristic time τSE and dispersion parameter β). In this study, a clearly different (one-parameter) analytic function is obtained from a microscopic model based on the formation of metastable H (MSH) atoms in a-Si:H films. Assuming that MSH atoms are the only mobile species, only three chemical reactions are significant : MSH are produced from doubly hydrogenated (SiH HSi) configurations and trapped either at broken bonds or Si-H bonds, corresponding respectively to light-induced annealing (LIA) and light-induced creation (LIC) of defects. Competition between trapping sites results in a saturation of N(t) at a steady-state value Nss. A one-parameter fit of this analytical function to experimental data is generally good, indicating that the use of a statistical distribution of trap energies is not necessary.

Comparison of Current and Light Induced Defects in a-Si:H

1993 ◽  
Vol 297 ◽  
Author(s):  
R.A. Street ◽  
W.B. Jackson ◽  
M. Hack
Keyword(s):  
Numerical Modelling ◽  
Reverse Bias ◽  
Defect Density ◽  
Reverse Current ◽  
Bias Current ◽  
Spatial Profile ◽  
Forward Current ◽  
Defect Creation ◽  
Induced Defects ◽  
Metastable Defect

Metastable defect creation by illumination and by a forward current in p-i-n devices are compared using CPM and reverse current measurements of the defect density. The data show that the same defects are formed by the two mechanisms, but with different spatial profiles. Numerical modelling shows how the spatial profile influences the reverse bias current.

Saturation of Metastable-Defect Density in a-Si:H

1990 ◽  
Vol 192 ◽  
Author(s):  
David Redfield ◽  
Richard H. Bube
Keyword(s):  
Steady State ◽  
Defect Density ◽  
Atomic Model ◽  
Transient Responses ◽  
Induced Defects ◽  
Metastable Defect

ABSTRACTThe existence of saturation (or steady state) in the density of light-induced defects in amorphous Si:H is shown to have major importance for the interpretation of the nature and origin of these defects. First, a number of characteristics of the steady-state and transient responses to light and temperature are described and contrasted. These lead to the conclusion that the saturation value is the only useful criterion of the number of defects in these materials. We then describe a new atomic model for defects, unifying both dopant-induced and light-induced defects. This model invokes foreign atoms in defects, and saturation reflects the limitation imposed by the numbers of such atoms. Many other observed properties of defects are explained by this model.

Pulsed-Light-Induced Metastable Defect Creation in Hydrogenated Amorphous Silicon

1995 ◽  
Vol 377 ◽  
Author(s):  
Jong-Hwan Yoon ◽  
H. L. Kim
Keyword(s):  
Time Dependence ◽  
Amorphous Silicon ◽  
Defect Density ◽  
Hydrogenated Amorphous Silicon ◽  
Pulsed Light ◽  
Illumination Time ◽  
Defect Creation ◽  
Annealing Rate ◽  
Hydrogenated Amorphous ◽  
Metastable Defect

ABSTRACTWe report the results of a study of metastable defect creation by pulsed light soaking in undoped hydrogenated amorphous silicon (a-Si:H). An illumination time dependence of the defect density, a saturated defect density, and light-induced annealing under pulsed laser light have been studied. Measurements show approximately a t1/2 time-dependence of the defect creation, which is independent of light intensity. It is observed that the saturation value of the defect density is about one order of magnitude higher than by cw illumination in device quality films. It has been suggested that these results would be due to the difference in the light-induced defect annealing rate between cw and pulsed lights, in which it is found that the light-induced annealing rate by pulsed light is lower than by cw light.

Photodegradation in a-Si:H Prepared by Hot-Wire CVD as a Function of Substrate and Filament Temperatures

2000 ◽  
Vol 609 ◽  
Author(s):  
Daxing Han ◽  
Guozhen Yue ◽  
Jing Lin ◽  
Hitoe Habuchi ◽  
Eugene Iwaniczko ◽  
...  
Keyword(s):  
Activation Energy ◽  
Substrate Temperature ◽  
Density Of States ◽  
Electron Mobility ◽  
Defect Density ◽  
Degradation Kinetics ◽  
Hot Wire ◽  
Conductivity Activation Energy ◽  
Charged Defects ◽  
Metastable Defect

ABSTRACTWe have studied light-soaking effects, such as photoconductivity (PC) degradation kinetics, the changes of conductivity activation energy, Ea, and the defect density of states (DOS) in a-Si:H films deposited by hot-wire CVD. Films were deposited in a substrate temperature range from 280 to 440 °C for filament temperatures of 1900 and 2100 °C. We find that (a) the photodegradation kinetics does not follow the stretched exponential rule for all of the samples; (b) the Fermi level position moves up after light-soaking for most samples; and (c) the metastable defect DOS deduced from sub-band gap absorption is not consistent with that deduced from the electron mobility-lifetime product. The results are discussed according to the possible mechanism in which charged defects exist in hot-wire a-Si:H films.a

Metastable Defect Formation by Hydrogen Relocation and Rebonding

1995 ◽  
Vol 377 ◽  
Author(s):  
Qiming Li ◽  
R. Biswas
Keyword(s):  
Defect Formation ◽  
Defect Density ◽  
Tight Binding ◽  
Rate Equations ◽  
Dangling Bond ◽  
Defect Formation Energy ◽  
Fundamental Process ◽  
Induced Defects ◽  
Metastable Defect ◽  
Density Rate

ABSTRACTMolecular dynamics with the tight-binding approach are utilized to examine the fundamental process of dangling bond creation via the rebonding of H from Si-H bonds to weak Si-Si bonds. The defect formation energy is found to strongly correlate with the bond-length of the weak Si-Si bond, indicating that the distribution of weak Si-Si bonds controls the total defect density. Rate equations for thermally generated and light-induced defects are developed and utilized to calculate the equilibrium and saturated defect density. The results agree well with experimental data.

Thermal Equilibrium, Metastable and Irreversible Defects in a-Si:H

1989 ◽  
Vol 149 ◽  
Author(s):  
R. A Street ◽  
K. Winer
Keyword(s):  
Relaxation Time ◽  
Low Temperature ◽  
Temperature Dependence ◽  
Thermodynamic Model ◽  
Thermal Equilibrium ◽  
Defect Density ◽  
Defect States ◽  
Different Types ◽  
Metastable Defect ◽  
Deposition Conditions

ABSTRACTMeasurements are reported of metastable defect states in undoped a-Si: H, with the aim of understanding the relation between the different types of metastability. The temperature dependence of the thermal equilibrium defect density agrees well with a proposed thermodynamic model and their relaxation time varies with deposition conditions. The rate of light induced defect creation and annealing in samples deposited at low temperature and with a large initial defect density, decreases progressively as the irreversible defects are removed by annealing.

Coupled Effects of Light and Temperature on Degradation of a-Si:H

1991 ◽  
Vol 219 ◽  
Author(s):  
Lisa E. Benatar ◽  
Michael Grimbergen ◽  
David Redfeeld ◽  
Richard H. Bube
Keyword(s):  
Steady State ◽  
Defect Formation ◽  
Defect Density ◽  
Hydrogenated Amorphous Silicon ◽  
Gradual Change ◽  
State Behavior ◽  
Excitation Rate ◽  
Barrier Heights ◽  
Hydrogenated Amorphous ◽  
Metastable Defect

ABSTRACTThe effects of excitation rate and temperature on the kinetics and steady-state behavior of metastable defect formation in hydrogenated amorphous silicon (a-Si:H) have been studied. The dependences on temperature of the lifetime, τ, and stretching parameter, β, from a stretched exponential description of the kinetics were measured for one sample. We do not see a linear dependence of β on temperature over die entire temperature range studied (270K–370K), and τ increases monotonically with decreasing temperature. Steady-state results show defect density to be dependent on bodi temperature and excitation rate over the ranges measured (from 395K to 470K and from 6 × 1020 to 2 × 1022 s-l cm-3). The gradual change in temperature dependence is explained by a distribution of barrier heights between the ground and metastable states.

Relaxation of Electron Beam-Induced Metastable Defects in a-Si:II

1993 ◽  
Vol 297 ◽  
Author(s):  
M. Grimbergen ◽  
R. Mcconville ◽  
D. Redfield ◽  
R.H. Bube
Keyword(s):  
Activation Energy ◽  
Electron Beam ◽  
Amorphous Silicon ◽  
Time Constant ◽  
Electron Irradiation ◽  
Defect Density ◽  
Initial Density ◽  
Induced Defects ◽  
Metastable Defect

Relaxation of the metastable defect density in undoped amorphous silicon is observed after keV electron irradiation. The time constant for relaxation has an activation energy close to 1 eV, similar to that for light-induced defects. Relaxation appears to follow two or more stages. A large initial density relaxes rapidly, followed by slower relaxation more characteristic of light-induced defects. Separation of these components allows for a better comparison of e-beam and light-induced saturation defect density.

The Effect of Post-Deuteration on Metastability in a-Si:H

1993 ◽  
Vol 297 ◽  
Author(s):  
N.H. Nickel ◽  
W.B. Jackson ◽  
C.C. Tsai
Keyword(s):  
Defect Formation ◽  
Chemical Potential ◽  
Defect Density ◽  
Hydrogenated Amorphous Silicon ◽  
Dangling Bond ◽  
Deuterium Plasma ◽  
Bond Density ◽  
Intense Light ◽  
Hydrogenated Amorphous ◽  
Metastable Defect

Hydrogenated amorphous silicon films were deuterated through a sequence of 1h exposures to a remote deuterium plasma at 350°C. The concentration profiles of hydrogen and deuterium were determined by SIMS at various times during the exposure sequence. The defect density in state A, after deuteration and after illumination with white light were determined using CPM measurements following each 1h exposure sequence. We find that post-deuteration does not alter the defect density in state A, change the Urbach edge, nor significantly alter metastable defect formation. Intense light soaking increases the defect density by about 5 × 10l6cm−3 independent of the total H + D concentration. These results suggest that D always enters the sample in pairs pinning the hydrogen chemical potential which supports the idea of a negative U system for hydrogen and deuterium. Despite an increase of Si-H bonds by as much as 3 × 1021cm−3, the annealed dangling bond density and the weak Si-Si bond density did not change.This suggests that the density of weak Si-Si bonds as well as the dangling bond density is determined by equilibration with strong Si-Si bonds through the interchange of H. The implications of these results for H bonding will be discussed.

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