Vis-NIR characteristics of amorphous germanium films and electrical properties of a-Ge/p-Si heterostructures obtained by pulsed-laser deposition method

Abstract

Optical properties of a-Ge films (glass substrate) and electrical properties of a-Ge/p-Si heterostructures obtained by the pulsed-laser deposition method have been studied. It is shown that optical properties of a-Ge films can be well explained by the Tauc model for amorphous semiconductors. The dependence of optical gap on the film thickness is obtained for a-Ge films. Forward-bias current-voltage characteristics of the a-Ge/p-Si heterostructures are satisfactorily approximated by the relation for current density J = CVm, where m varies from 1.45 to 1.95 depending on the applied forward bias and a-Ge film thickness. Also, for the mentioned heterostructure (a-Ge film thickness is 400 nm) nearly quadratic dependence of the current density is observed, which indicates the predominance of the space-charge-limited current.