Correlation of optical and thermal emission processes for bound-to-free transitions from mobility gap states in doped hydrogenerated amorphous silicon

1984 ◽  
Author(s):  
A. V. Gelatos ◽  
J. D. Cohen ◽  
J. P. Harbison
Keyword(s):  
Amorphous Silicon ◽  
Thermal Emission ◽  
Gap States ◽  
Mobility Gap

Configurational Relaxation of the D Defect in Hydrogenated Amorphous Silicon as a Function of Fermi Energy

1992 ◽  
Vol 258 ◽  
Author(s):  
Thomas M. Leen ◽  
Randall J. Rasmussen ◽  
J. David Cohen
Keyword(s):  
Amorphous Silicon ◽  
Fermi Energy ◽  
Thermal Emission ◽  
Scaling Law ◽  
Hydrogenated Amorphous Silicon ◽  
Dangling Bond ◽  
Universal Scaling ◽  
Depletion Width ◽  
Hydrogenated Amorphous ◽  
Optical Evidence

ABSTRACTBy using light soaking and partial dark annealing to vary the Fermi level in n-type a-Si:H, we have examined the thermal emission of electrons from the dangling bond (D) defect. We find optical evidence for a change in the configuration of the D defect when EF = Ec-0.55±0.08eV. We find that the relaxation rate increases with temperature and increases as EF is brought closer to Ec. Voltage-pulse photocapacitance and depletion-width-modulated ESR show emission is predominantly from D° defects for short emission times and short filling pulse widths. With longer emission times and longer filling pulse widths, emission from D-dominates. We also find that the charge emission transient fits a universal scaling law under a variety of pulsing conditions, temperatures, and anneal states.

Structural Relaxation and Structural Memory at Amorphous Silicon Dangling Bonds

1994 ◽  
Vol 336 ◽  
Author(s):  
Howard M. Branz ◽  
Peter A. Fedders
Keyword(s):  
Amorphous Silicon ◽  
Energy Levels ◽  
Electronic Energy ◽  
Relaxation Effects ◽  
Structural Environment ◽  
Slow Relaxations ◽  
Transient Capacitance ◽  
Electronic Energy Levels ◽  
Gap States ◽  
Structural Memory

ABSTRACTWe examine the energy and time scales of configurational relaxation around the dangling bond defect, D, in hydrogenated Amorphous silicon (a-Si:H). After D captures or emits charge, its bond angle, electron energy eigenvalues and local structural environment all change. This determines the measured electronic energy levels; we use previous theoretical results and experimental data to estimate the density of gap states in the different atomic configurations of D. We also describe D relaxation effects observed in experiments, including the very slow relaxations found in recent transient capacitance measurements. To explain the unusual T-independent kinetics of transient capacitance carrier emission, we propose a model of “structural memory” in a-Si:H. After carrier capture, neighbors of D retain memory of their pre-capture configuration for seconds at 300K. The rate-limiting step to carrier emission is an effectively one-dimensional random walk of these neighbors through their configuration space and back to the pre-capture configuration. The final, activated, step of emission is very rapid. We describe analytic and monte Carlo calculations that support the structural memory Model and propose possible microscopic Mechanisms.

Stability in Amorphous Silicon

1987 ◽  
Vol 95 ◽  
Author(s):  
Z E. Smith ◽  
S. Wagner
Keyword(s):  
Electron Spin Resonance ◽  
Amorphous Silicon ◽  
Hydrogenated Amorphous Silicon ◽  
Thermal Recovery ◽  
Defect States ◽  
Spin Resonance ◽  
Resonance Data ◽  
Electron Spin Resonance Data ◽  
Gap States ◽  
Hydrogenated Amorphous

AbstractThe experimental phenomena associated with light-induced degradation and thermal recovery of hydrogenated amorphous silicon (a-Si:H) films are reviewed, with special emphasis on the limitations of each experimental technique. When several techniques are used in concert, a fuller picture emerges. Recent experiments suggest different positions in the band-gap of the paramagnetic-associated defect states (the dangling bonds) for doped and undopedfilms; this information can be combined with conductivity, sub-bandgap optical absorption and electron spin resonance data to yield a model for the density of gap states (DOS) in a- Si:H, including how the DOS changes upon illumination and annealing.

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