Evolution of Charged Gap Statesin a- Si:H Under Light Exposure

2003 ◽  
Vol 762 ◽  
Author(s):  
M. Zeman ◽  
V. Nádaždy ◽  
R.A.C.M.M. van Swaaij ◽  
R. Durný ◽  
J.W. Metselaar
Keyword(s):  
Deep Level ◽  
Light Exposure ◽  
Dark Conductivity ◽  
Initial Energy ◽  
Energy Distributions ◽  
Transient Spectroscopy ◽  
Induced Changes ◽  
Hydrogenated Amorphous ◽  
Kinetics Of ◽  
Positively Charged

AbstractThe charge deep-level transient spectroscopy (Q-DLTS) experiments on undoped hydrogenated amorphous silicon (a-Si:H) demonstrate that during light soaking the states in the upper part of the gap disappear, while additional states around and below midgap are created. Since no direct correlation is observed in light-induced changes of the three groups of states that we identify from the Q-DLTS signal, we believe that we deal with three different types of defects. Positively charged states above midgap are related to a complex formed by a hydrogen molecule and a dangling bond. Negatively charged states below midgap are attributed to floating bonds. Various trends in the evolution of dark conductivity due to light soaking indicate that the kinetics of light-induced changes of the three gap-state components depend on their initial energy distributions and on the spectrum and intensity of light during exposure.

Effect of Fermi Level Position in Intrinsic a-Si:H on the Evolution of Defect States under Light Exposure.

2005 ◽  
Vol 862 ◽  
Author(s):  
M. Zeman ◽  
V. Nádaždy ◽  
R. Durný ◽  
J.W. Metselaar
Keyword(s):  
Deep Level ◽  
Light Exposure ◽  
Oxide Semiconductor ◽  
Defect State ◽  
Defect States ◽  
State Distribution ◽  
Type Distribution ◽  
Transient Spectroscopy ◽  
Hydrogenated Amorphous ◽  
Positively Charged

AbstractThe evolution of the programmed defect-state distributions in intrinsic hydrogenated amorphous silicon (a-Si:H) due to light soaking was qualitatively determined from charge deep-level transient spectroscopy. The defect-state distribution in a-Si:H was programmed by applying a particular bias voltage on the metal-oxide-semiconductor structure while annealing the structure above the equilibration temperature. The programmed distributions simulate defect-state distributions in different parts of an actual a-Si:H solar cell, particularly in the intrinsic regions close to the p/i and i/n interfaces.The defect-state distribution in the bulk of the intrinsic layer is characterized by comparable contributions from the positively charged defect states above midgap, Dh, neutral states, Dz, and negatively charged states below midgap, De. In the programmedp-type (n-type) defect-state distribution there is an excess of the Dh (De) states. Light exposure modifies the p-type distribution that evolves to a broad distribution of states with a maximum around midgap. This distribution is dominated by Dz states with substantial contributions from Dh and De states. In case of n-type distribution light soaking only slightly influences the distribution by removing a part of the Dh states and by a small increase of Dz and De states.

The Role of Charged Gap States in Light-Induced Degradation of Single-Junction a-Si:H Solar Cells

2004 ◽  
Vol 808 ◽  
Author(s):  
M. Zeman ◽  
V. Nádazdy ◽  
J.W. Metselaar
Keyword(s):  
Solar Cells ◽  
Deep Level ◽  
Spectral Response ◽  
State Density ◽  
Single Junction ◽  
Transient Spectroscopy ◽  
Gap States ◽  
Hydrogenated Amorphous ◽  
Positively Charged

ABSTRACTComputer simulations of single-junction hydrogenated amorphous silicon (a-Si:H) solar cells with different thickness of the intrinsic layer were carried out in order to study the role of charge gap states in their light-induced degradation. It is demonstrated that it is the decrease of positively charged states above midgap, Dh, and the increase of neutral states around midgap,Dz, and negatively charged states below midgap, De in the intrinsic layer that result in a drop of performance of the solar cells due to light soaking. These changes in the gap states are in accordance with our recent experimental results from the charge deep-level transient spectroscopy on undoped a-Si:H. The experimentally observed changes in the dark and illuminated J-V curves and spectral response could not be simulated with the same set of input parameters by only increasing the defect-state density in the intrinsic layer.

Persistent Photoconductivity And Thermal Recovery Kinetics Of Low Energy Ar + Bombarded GaAs

1991 ◽  
Vol 223 ◽  
Author(s):  
A. Vaseashta ◽  
L. C. Burton
Keyword(s):  
Deep Level Transient Spectroscopy ◽  
Deep Level ◽  
Thermal Recovery ◽  
Low Energy ◽  
Persistent Photoconductivity ◽  
Transport Parameters ◽  
Excellent Correlation ◽  
Proposed Model ◽  
Transient Spectroscopy ◽  
Kinetics Of

ABSTRACTKinetics of persistent photoconductivity, photoquenching, and thermal and optical recovery observed in low energy Ar+ bombarded on (100) GaAs surfaces have been investigated. Rate and transport equations for these processes were derived and simulated employing transport parameters, trap locations and densities determined by deep level transient spectroscopy. Excellent correlation was obtained between the results of preliminary simulation and the experimentally observed values. The exponential decay of persistent photoconductivity response curve was determined to be due to metastable electron traps with longer lifetime and is consistent with an earlier proposed model.

scholarly journals Kinetics of silver photodiffusion into amorphous S-rich germanium sulphide – neutron and optical reflectivity

2019 ◽  
Vol 91 (11) ◽  
pp. 1821-1835 ◽  
Author(s):  
Yoshifumi Sakaguchi ◽  
Hidehito Asaoka ◽  
Maria Mitkova
Keyword(s):  
Reaction Layer ◽  
Electronic Band Structure ◽  
Light Exposure ◽  
Neutron Reflectivity ◽  
Electronic Band ◽  
Reflectivity Measurement ◽  
Optical Reflectivity ◽  
Amorphous Chalcogenides ◽  
Induced Changes ◽  
Kinetics Of

Abstract Silver photodiffusion is one of the attractive photo-induced changes observed in amorphous chalcogenides. In this research, we focus on amorphous S-rich germanium sulphide and study the kinetics of the silver photodiffusion by neutron reflectivity, as well as optical reflectivity. It was found from the neutron reflectivity profiles with 30 s time resolution that silver dissolved into the germanium sulphide layer, forming a metastable reaction layer between the Ag and the germanium sulphide layers, within 2 min of light exposure. Subsequently, silver slowly diffused from the metastable reaction layer to the germanium sulphide host layer until the Ag concentration in both layers became identical, effectively forming one uniform layer; this took approximately 20 min. Optical reflectivity reveals the electronic band structure of the sample, complementary to neutron reflectivity. It was found from the optical reflectivity measurement that the metastable reaction layer was a metallic product. The product could be Ag8GeS6-like form, which is regarded as the combination of GeS2 and Ag2S, and whose backbone is composed of the GeS4 tetrahedral units and the S atoms. We attribute the first quick diffusion to the capture of Ag ions by the latter S atoms, which is realised by the S–S bond in amorphous S-rich germanium sulphide, while we attribute the second slow diffusion to the formation of the Ag–Ge–S network, in which Ag ions are captured by the former GeS4 tetrahedral units.

Electrical and Electrochemical Properties of a-C:N:H Films

1999 ◽  
Vol 593 ◽  
Author(s):  
Yu.V. Pleskov ◽  
M.D. Krotova ◽  
V.I. Polyakov ◽  
A.V. Khomich ◽  
A.I. Rukovishnikov ◽  
...  
Keyword(s):  
Point Defects ◽  
Electrochemical Impedance ◽  
Deep Level ◽  
Ion Beam ◽  
Plasma Source ◽  
Inductively Coupled ◽  
Active Point ◽  
Transient Spectroscopy ◽  
Quartz Substrates ◽  
Kinetics Of

ABSTRACTElectrochemical impedance in H2SO4 solutions and kinetics of redox reactions in the Fe(CN)63-/4- system were studied on amorphous nitrogenated diamond-like carbon (a-C:N:H) thin-film electrodes. Parameters of point defects (trapping centers) were also measured by the Deep Level Transient Spectroscopy techniques. The films have been fabricated on p- and i-type silicon and quartz substrates, using direct ion beam deposition from an RF inductively coupled N2+ CH4 plasma source. The increase in N2/CH4 ratio in the gas mixture lead to a decrease in the electrical resistivity and optical bandgap of the films from 3×1010to 5×106 Ω cm and from 1.3 to 0.6 eV, respectively. Simultaneously, the concentration of electrically active point defects increased significantly and the charge transfer at the a-C:N:H film/redox electrolyte interface was facilitated

A Comparative Study of Defect States in Light-Soaked and High-Temperature-Annealed a-Si:H

1993 ◽  
Vol 297 ◽  
Author(s):  
Z. M. Saleh ◽  
H. Tarui ◽  
S. Tsuda ◽  
S. Nakano ◽  
Y. Kuwano
Keyword(s):  
High Temperature ◽  
Light Exposure ◽  
Dark Conductivity ◽  
Defect States ◽  
Narrow Component ◽  
Spin Resonance ◽  
The Difference ◽  
Increasing Temperature ◽  
Induced Changes ◽  
Induced Defects

Our previous results of light-induced electron spin resonance (LESR) indicate that, in hydrogenated amorphous silicon (a-Si:H), light-induced defects differ from those formed during deposition or high-temperature annealing. A plausible interpretation, in which light-induced defects occupy higher-energy states, was proposed to explain these differences. In this study, the constant photocurrent method (CPM), dark conductivity and steady-state (SS) LESR are used to supply new evidence for the difference and conduct two important tests on our hypothesis. In striking agreement with our predictions, we find that the light-induced changes in the SS-LESR lineshape (a decrease in the narrow component relative to the broad one upon light exposure) become indeed more dramatic as the demarcation energies move closer to the midgap by increasing temperature or decreasing bias-light intensity for SS-LESR.

scholarly journals Electrically Active Defects In Solar Cells Based On Amorphous Silicon/Crystalline Silicon Heterojunction After Irradiation By Heavy Xe Ions

2015 ◽  
Vol 66 (6) ◽  
pp. 323-328 ◽  
Author(s):  
Ladislav Harmatha ◽  
Miroslav Mikolášek ◽  
L’ubica Stuchlíková ◽  
Arpád Kósa ◽  
Milan Žiška ◽  
...  
Keyword(s):  
Amorphous Silicon ◽  
Heavy Ions ◽  
Deep Level Transient Spectroscopy ◽  
Crystalline Silicon ◽  
Deep Level ◽  
Different Types ◽  
Radiation Induced ◽  
Transient Spectroscopy ◽  
Induced Defects ◽  
Hydrogenated Amorphous

Abstract The contribution is focused on the diagnostics of structures with a heterojunction between amorphous and crystalline silicon prepared by HIT (Heterojunction with an Intrinsic Thin layer) technology. The samples were irradiated by Xe ions with energy 167 MeV and doses from 5 × 108 cm−2 to 5 × 1010 cm−2. Radiation defects induced in the bulk of Si and at the hydrogenated amorphous silicon and crystalline silicon (a-Si:H/c-Si) interface were identified by Deep Level Transient Spectroscopy (DLTS). Radiation induced A-centre traps, boron vacancy traps and different types of divacancies with a high value of activation energy were observed. With an increased fluence of heavy ions the nature and density of the radiation induced defects was changed.

Hydrogen and Lithium Passivation of Gold in Silicon: A Comparative Study

1995 ◽  
Vol 378 ◽  
Author(s):  
E. ö. Sveinbjörnsson ◽  
S. Kristjansson ◽  
O. Engström ◽  
H. P. Gislason
Keyword(s):  
Complex Formation ◽  
Deep Level Transient Spectroscopy ◽  
Deep Level ◽  
Opposite Charge ◽  
Active Complex ◽  
Capacitance Voltage ◽  
Transient Spectroscopy ◽  
Kinetics Of ◽  
Secondary Ion ◽  
Coulomb Attraction

AbstractWe report studies of passivation of the gold center in silicon by hydrogen and lithium using deep level transient spectroscopy (DLTS), capacitance voltage (CV) profiling and secondary ion mass spectroscopy (SIMS). Both lithium and hydrogen are able to remove the electrical activity of the gold center from the silicon band gap but the passivation mechanisms are different. In the case of lithium the passivation is most likely due to a Coulomb attraction between lithium donors Li+ and gold acceptors Au−. No complex formation is observed between Li+ and Au0. In contrast, hydrogen is able to passivate the gold center without the need of opposite charge states of the species involved. Two Au-H complexes are observed, one (G) electrically active, and another (PA) passive. Based on the annealing kinetics of these complexes we propose that the active complex is a Au-H pair and that the passive complex contains two H atoms (Au-H2).

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