Shift of Optical Absorption Edgesin Transparent Conducting Films
Zhang Deheng ( Department of Physics, Shandong University, Jinan, 250100)
The band energy gap, Eg, for a semiconductor is determined not only by the atom content and the bond stases of composing atoms, but also affected by the defects and externally doping. More important. is that the band gap is a function of carrier concentration. In this paper we review the investigation results about the relationship between optical gap and carrier concentration in transparent conducting films ( ZnO, SnO2, In2O3). One aspect, high carrier concentration shifts the Fermi level into the conduction band and subsequently a Burstein Shift occurs which widens the band gap . Another aspect, the self-energy produced by many-body-effect between electrical charges and overlap of the conduction band and impurity band shrinkage the band gap .