The defect density of B‐doped a‐Si: H samples prepared by magnetic field assisted high deposition rate chemical vapor deposition is investigated by the constant photocurrent method (CPM). For doping the alternative unpoisonous triethylboron (TEB) is successfully utilized. Furthermore, the dark conductivity σD and the optical parameters Tauc gap Eg, Tauc slope B, and Urbach energy E0 are determined. Eg and B do not vary within the range of doping but depend on the deposition rate. By deconvolution of the CPM spectra using a new procedure it is shown that the true valence band tail slope ET differs from E0. Both E0 and ET as well as the defect concentration Ndb0 reach a minimum at compensation which can be monitored by a minimum in σD. An analysis of the energetic distribution of the localized states is possible by assuming exponential tails and Gaussian defect distributions. The results are qualitatively and quantitatively analyzed on the base of the hydrogen mediated weak bond/dangling bond conversion model and the defect pool model. They show a very good agreement especially for the p‐type samples.
The degration of the photoelectrical properties of a‐Si: H films grown by PECVD at different deposition conditions (reactor geometry, deposition rate) is investigated by irradiation of the samples with 20 keV electrons or light (AM 1). The dark‐ and photoconductivity as well as CPM are used to monitor the change of the sample properties during degradation and annealing. Using a multiple magnetic field assisted PECVD in coaxial geometry it is possible to increase the deposition rate at reduced degradation level. Significant differences between light and electron degradation cannot be obtained. It is found that with decreasing hydrogen content the stability of the photoelectrical properties can be improved. The measured CPM spectra are evaluated with respect to the localized gap DOS in dependence on the degradation level. The applied deconvolution procedure reveals a fixed position of the created defects (D−‐level) and in spite of the increasing slope of the Urbach tail E0 a constant slope of the valence‐band tail ET.
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