Temperature Dependence of the Decay of Optically Excited Charge Carriers in Amorphous Silicon

2003 ◽  
Vol 762 ◽  
Author(s):  
J. Whitaker ◽  
P. C. Taylor
Keyword(s):  
Temperature Dependence ◽  
Amorphous Silicon ◽  
State Density ◽  
Charge Carriers ◽  
Band Tail ◽  
Spin Resonance ◽  
Recombination Processes ◽  
Long Time ◽  
Tail Structure ◽  
Kinetics Of

AbstractWe report the temperature dependence of the growth and decay of the optically induced electron spin resonance (LESR) on short and long time scales (10-3 s < t < 2500 s). This range of times spans the region between previously published photoluminescence and the LESR data. In addition, we examine the steady-state density of optically excited charge carriers as a function of temperature. These measurements lead to a better understanding of the band tail structure of amorphous silicon as well as the kinetics of the excitation and recombination processes.

Low Temperature Kinetics for the Growth and Decay of Band-Tallcarriers and Dangling Bonds in Hydrogenated Amorphous Silicon

1999 ◽  
Vol 557 ◽  
Author(s):  
Niko Schultz ◽  
P.C. Taylor
Keyword(s):  
Amorphous Silicon ◽  
Hydrogenated Amorphous Silicon ◽  
Underlying Mechanism ◽  
Total Production ◽  
Dangling Bonds ◽  
Band Tail ◽  
Thermally Activated ◽  
Spin Resonance ◽  
Hydrogenated Amorphous ◽  
Kinetics Of

AbstractIn hydrogenated amorphous silicon (a-Si:H), the kinetics of the light induced production of silicon dangling bonds and long-lived band-tail electrons and holes has been measured at temperatures between 65 and 340 K using light induced electron spin resonance (LESR). Below about 150 K the measurement of Si dangling bonds is masked by the accumulation of long-lived band-tail carriers. The kinetics of the growth and decay of these long-lived, trapped band-tail carriers consists of very fast components (τ < ms) and very long components (τ > h). Optical quenching of these long-lived carriers is not efficient at quenching energies of 0.6 eV. Afler removal of these long-lived band tail carriers by annealing at about 250 K we find that the total production of silicon dangling bonds at 65 K after 10 h of illumination is about a factor of five less than at 340 K. The dangling bond production resulting from 10 h of illumination is well fit to an underlying mechanism that, if thermally activated, exhibits an activation energy of approximately 10 meV.

Magnetic Resonance Probes Of Band Tail States And Defects In Tetrahedrally Coordinated Amorphous Semiconductors

2002 ◽  
Vol 715 ◽  
Author(s):  
P. C. Taylor
Keyword(s):  
Amorphous Silicon ◽  
Hydrogenated Amorphous Silicon ◽  
Amorphous Semiconductors ◽  
Dangling Bonds ◽  
Band Tail ◽  
Wide Range ◽  
Recombination Processes ◽  
Staebler Wronski Effect ◽  
Hydrogenated Amorphous ◽  
Kinetics Of

AbstractRecent electron spin resonance (ESR) results relating to (1) recombination processes for optically excited electrons and holes in tetrahedrally coordinated amorphous semiconductors and (2) kinetics of metastable defects (dangling bonds associated with the Staebler-Wronski effect) in hydrogenated amorphous silicon (a-Si:H). With regard to recombination processes, ESR measurements have been performed over a wide range of excitation intensities (nW/cm2 to W/cm2) on hydrogenated amorphous silicon (a-Si:H) and hydrogenated amorphous germanium (a-Ge:H). The kinetics can be studied down to carrier densities as low as 1014 cm-3. The longtime decay curves show that at large carrier separation (1) the random distribution of optically excited electrons and holes is subject to the condition of charge neutrality, and (2) the decays are universal and independent of the densities of localized, band-tail states. With regard to the metastable defects in a-Si:H, the kinetics of the production and thermal annealing of silicon dangling bonds have been measured at temperatures between 25 and 480 K using ESR. Below about 150 K the measurement of the dangling bonds is masked by long-lived, band tail carriers that accumulate with time. The production rate for silicon dangling bonds decreases with decreasing temperature and is nearly temperature independent below approximately 100 K. Defects created by 10 hours of irradiation below 100 K anneal almost completely at 300 K. In a- Ge:H, the first measurements of optically induced, metastable germanium dangling bonds have been made.

Electron Spin Resonance Studies of Amorphous Silicon

1980 ◽  
Vol 3 ◽  
Author(s):  
David K. Biegelsen
Keyword(s):  
Electron Spin Resonance ◽  
Amorphous Silicon ◽  
Electron Spin ◽  
Amorphous Semiconductor ◽  
Experimental Techniques ◽  
Equilibrium Behavior ◽  
Spin Resonance ◽  
Recombination Processes ◽  
Simple Picture ◽  
Non Equilibrium

ABSTRACTElectron spin resonance and related spin dependent measurements have been used to make key contributions to the understanding of amorphous silicon, specifically as probes of the dominant states in the gap, recombination processes and doping. In this paper we give a cursory description of the techniques as they apply to this problem. We then review what has been learned in a-Si:H usually from coupled results of spin resonance and other complementary experimental techniques. The results lead us to a surprisingly simple picture of the equilibrium and non-equilibrium behavior of defects and carriers in this prototypical amorphous semiconductor.

Temperature Dependence of the Photoinduced Degradation and Annealing in a-Si:H

2000 ◽  
Vol 609 ◽  
Author(s):  
Niko Schultz ◽  
P. Craig Taylor
Keyword(s):  
Temperature Dependence ◽  
Room Temperature ◽  
Dangling Bond ◽  
Defect States ◽  
Slow Increase ◽  
Spin Resonance ◽  
The Difference ◽  
Kinetics Of ◽  
Defect Densities ◽  
Spin Densities

ABSTRACTWe investigated the temperature dependence of the production and annealing kinetics of the light induced defect states in a:Si:H by electron spin resonance (ESR). At low temperatures (T ∼ 25 K) the silicon dangling bond production is about half as efficient as it is at 300 K. Defects, which are created below about 100 K, almost entirely anneal at room temperature. A sample of a-Si:H, which is subjected to several photo-excitation and annealing cycles, shows a very slow increase of both the degraded and annealed defect densities. The difference in the spin densities between the annealed and degraded states decreases with an increasing number of degradation/annealing cycles.

Hydrogenated Amorphous Silicon Alloyed with Selenium

1998 ◽  
Vol 507 ◽  
Author(s):  
Shenlin Chen ◽  
P. C. Taylor ◽  
J. M. Viner
Keyword(s):  
Amorphous Silicon ◽  
Vapor Deposition ◽  
Hydrogenated Amorphous Silicon ◽  
Chemical Vapor ◽  
Band Tail ◽  
Photothermal Deflection Spectroscopy ◽  
Spin Resonance ◽  
Photo Conductivity ◽  
Photothermal Deflection ◽  
Hydrogenated Amorphous

ABSTRACTHydrogenated amorphous silicon alloyed with selenium has been made by plasma enhanced chemical vapor deposition (PECVD). The activation energy for electrical conduction is essentially unchanged for selenium concentrations < 1 at.%. The photo conductivity changes for selenium concentrations > 0.5 at. %. Photothermal deflection spectroscopy (PDS) and electron spin resonance (ESR), respectively, show that the width of the valence band tail states and the density of neutral silicon dangling bonds also change for selenium concentrations > 0.5 at. %.

Carrier Separation Effects in Doping Modulated Amorphous Silicon

1986 ◽  
Vol 70 ◽  
Author(s):  
J. Kakalios ◽  
C. C. Tsai ◽  
R. A. Street
Keyword(s):  
Amorphous Silicon ◽  
Charge Carriers ◽  
Silicon Films ◽  
Band Tail ◽  
Intensity Dependence ◽  
Pn Junction ◽  
In Doping ◽  
Decay Times ◽  
Photoconductivity Decay ◽  
Carrier Separation

ABSTRACTDoping modulated amorphous silicon films have been synthesized which exhibit photoconductivity decay times in excess of 1000 seconds at 78 K. The time and intensity dependence of the photoconductivity is described by a model in which photo-excited charge carriers are spatially separated to separate layers by the built-in pn junction fields and reside in band tail states.

Direct imaging of charge transfer

1996 ◽  
Vol 54 ◽  
pp. 680-681
Author(s):  
Yimei Zhu ◽  
J. Tafto
Keyword(s):  
Charge Transfer ◽  
Electron Diffraction ◽  
Scattering Amplitude ◽  
High Temperature Superconductors ◽  
Charge Carriers ◽  
Image Charge ◽  
Net Charge ◽  
Long Time ◽  
Electron Holes ◽  
First Time

The electron holes confined to the CuO2-plane are the charge carriers in high-temperature superconductors, and thus, the distribution of charge plays a key role in determining their superconducting properties. While it has been known for a long time that in principle, electron diffraction at low angles is very sensitive to charge transfer, we, for the first time, show that under a proper TEM imaging condition, it is possible to directly image charge in crystals with a large unit cell. We apply this new way of studying charge distribution to the technologically important Bi2Sr2Ca1Cu2O8+δ superconductors.Charged particles interact with the electrostatic potential, and thus, for small scattering angles, the incident particle sees a nuclei that is screened by the electron cloud. Hence, the scattering amplitude mainly is determined by the net charge of the ion. Comparing with the high Z neutral Bi atom, we note that the scattering amplitude of the hole or an electron is larger at small scattering angles. This is in stark contrast to the displacements which contribute negligibly to the electron diffraction pattern at small angles because of the short g-vectors.

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