Theoretical Study of the Optical-Absorption Edge in Amorphous Semiconductors

概要

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With a view to studying the properties of the optical-absorption edge in a-Si, wecalculate in the CPA the density of states (DOS), the absorption spectra and the spec-tral density on the basis of the site-disordered Abe-Toyozawa model. As the probabil-ity distribution for site disorder, we use the bilateral exponential distribution and thedistribution defined by an exponential factor with the fourth-order power in its argument as well as the common Gatussian distribution. Our assertioxt is that, to make themodel realistic, we must choose the degree of disorder small eutough relative to theband width such that we can identify the three regions of absorption with high, in-termediate and low energies. The intermediate region in this case universally shows anexponential behaviour, irrespective of the type of the probability distribution of"static" disorder. We compare the absorption spectra ICE ) calctxlated from the Kuboformula with the convolution 1....(E) in which the A-selection r'ule is completely reTaxed. We clarify the conditions under which 1...,(E) serves as a good approximationof I(E).
社団法人日本物理学会の論文
1988-05-15