Optical absorption above the optical gap of amorphous silicon hydride

✍ Scribed by G.D. Cody; B.G. Brooks; B. Abeles

• Book ID: 107905650
• Publisher: Elsevier Science
• Year: 1982
• Weight: 403 KB
• Volume: 8
• Category: Article
• ISSN: 0165-1633
• DOI: 10.1016/0165-1633(82)90065-x

✦ Synopsis

From transmission and reflection measurements on glow discharge prepared a-Si:Hx(x=0.09-0.19) films we obtain the imaginary part of the dielectric constant, e2 in the range 1.4 to 3.8 eV. We compare this data with the prediction of a model first introduced by Tauc for optical transitions, with momentum conservation relaxed, between the valence (occupied) and conduction (unoccupied) bands of an amorphous semiconductor. The agreement with the Tauc model is good, but is greatly improved if the constant momentum matrix element of that model is replaced by a constant dipole matrix element. This substitution, which is physically plausible for the high energy optical transitions considered, completely removes a spurious thickness dependence of the derived optical gap. We obtain from the modified Tauc model, an optical gap for a-Si:Hx(x=0.09-0.19) of 1.64 eV with a constant dipole matrix element of 6.7 A.