Optical Constants of Amorphous Ga₂Te₃ and In₂Te₃

Abstract

The optical response in amorphous (a-) Ga 2 Te 3 and In 2 Te 3 semiconductors in the 1.2–5.2-eV photon-energy range at room temperature has been measured by spectroscopic ellipsometry. These materials were obtained directly from the melt. It is found that the dielectric functions, ε ( E )= ε 1 ( E )+ i ε 2 ( E ), of a- Ga 2 Te 3 and a- In 2 Te 3 have a strong resemblance to those of amorphous tetrahedrally bonded semiconductors. The optical energy gap estimated from the plots of E ε 2 ( E ) 1/2 versus E is 1.2 eV for both a- Ga 2 Te 3 and a- In 2 Te 3 . Dielectric-related optical constants, such as the complex refractive index, absorption coefficient and normal-incidence reflectivity, of these amorphous semiconductors have also been presented.