Optical Properties of Non-Crystalline Semiconductors.
UTAH UNIV SALT LAKE CITY DEPT OF PHYSICS
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The optical properties of amorphous semiconductors are dominated by the presence of a tail on the optical absorption which falls exponentially into the spectral region which is normally transparent in crystalline solids. This so called Urbach edge is attributed to the presence of localized electronic states near the band edges in the amorphous semiconductors. Above the Urbach edge the absorption remains high due to the presence of interband electronic transitions just as those which occur in crystalline solids. Absent, however, are the singularities which are the result of the band structure in crystalline solids. Instead the amorphous semiconductors exhibit much smoother absorption spectra in the interband region. A very important question, for which a complete theoretical understanding remains elusive, is the position on the absorption edge which indicates where the major contribution changes from that due to localized to that due to extended electronic states.
- Solid State Physics