Investigation of a-Si:H thin films using the constant photocurrent method

Gap states of hydrogenated amorphous silicon near and above the threshold of microcrystallinity with subtle boron compensation

“…It is seen that the dependence of the E 0 in the light-soaked state ͑open triangle͒ on H dilution and B compensation follows the variation tendency of that in the annealed state. Although both the gap state density below E F and the E 0 value for all the samples are increased by illumination, similar to the earlier results, 13 their values in the light-soaked state for the diluted sample, particularly the appropriately compensated samples are much lower than those for the undiluted sample. Further, even more significant reduction of the density of gap states above E F in the light-soaked state was observed for the diluted samples without and with compensation.…”

“…The characteristic energy (E 0 ) of the Urbach valence bandtail was obtained from the exponential part of the absorption spectra, and was used to study the disorder in the a-Si:H network structure. 13 The relative gapstate distribution R0 n N(E) above E F could be calculated analytically by the procedure described previously, 11,12 where R0 is the effective recombination time of electrons which could be determined through measurements of steadystate photoconductivity, is the electron thermal velocity, a͒ Present address: Device Physics, Institute for Microstructural Sciences, National Research Council of Canada, Ottawa, Ontario K1A 0R6, Canada; electronic mail: shuran.sheng@nrc.ca. and n is the electron capture cross section.…”

Photocharge Transport and Recombination Measurements in Amorphous Silicon Films and Solar Cells by Photoconductive Frequency Mixing: Final Subcontract Report, 20 April 1998-30 June 2002

“…The Urbach energy E o was obtained from the exponential part of the absorption spectra. The Urbach tail is known to be due to bonding and thermal disorder in the material, and may be used to study the disorder in the network structure [27,28]. We can see that for pure a-Ge:H, there is strong sub-gap absorption due to high density of gap defect states below the Fermi level, but the Urbach energy E o is low, comparable to that for a-Si:H. With increasing Si content, the sub-gap absorption (or the gap-state density) is reduced significantly, while the Urbach energy E o is increased considerably, up to more than 90 meV at 44% Si in Ge, suggesting an increase in the compositional disorder.…”