The time evolution of the density of states in tritiated hydrogenated amorphous silicon.
Published: 2007
Language: eng
Number of pages: 231
ISBN-13: 9780494218402
Description: The dynamic defect pool model was used to predict the evolution of neutral dangling bonds (D0) with time. The results were found to be in agreement with previously reported Electron Spin Resonance data.Tritiated hydrogenated amorphous silicon (a-Si:H:T) thin films were deposited on crystalline silicon and high resistivity glass substrates. The time evolution of the density of defect states in these films was studied using the Constant Photocurrent Method (CPM) and Isothermal Capacitance Transient Spectroscopy (ICTS).The dynamic defect pool model was also used to predict the evolution of photoluminescence and of dark conductivity in a-Si:H:T. The results were found to agree with previously reported experimental data.A dynamic defect pool model was developed for a-Si:H:T, and the simulation results agreed with the experimental data for D+ and D -. The change in the D+ and D- concentrations was found to be, in main measure, the result of capture of the beta produced electrons in dangling bonds and weak bonds, with steady state achieved through the development of a balance between carrier generation and carrier capture processes.The ICTS results revealed that, following thermal annealing, the concentration of positively charged dangling bonds (D+) decreased over a period of 300 hours from 5&middot;1018 cm-3 to 1017 cm-3. The CPM results showed that the concentration of negatively charged dangling bonds (D-) increased over the same period of time from 5&middot;1017 cm-3  to 1020 cm-3. The D+ and D- concentrations were exponential functions of time but the rate was different than that of tritium decay. At the same time, the Urbach energy was found to decrease with time, from 120 meV to 60 meV. The decrease in the Urbach energy suggests a conversion of weak bonds, in the valence band tail, into dangling bonds.
Notes: Source: Dissertation Abstracts International, Volume: 68-01, Section: B, page: 0490.

Thesis (Ph.D.)--University of Toronto, 2006.

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