Optical and dielectric dispersion in the Ge/In2Se3/Ga2S3 interfaces

Abstract

In this article, the optical and dielectric performance of the Ge, Ge/In2Se3 and Ge/In2Se3/Ga2S3 interfaces are reported and discussed. The growth nature of the physically vacuum deposited thin film layers is investigated by means of X-ray diffraction and energy dispersive X-ray spectroscopy. Each 200 nm thick layer exhibited an amorphous type of crystallization with appropriate atomic stoichiometry. Optically, the Ge/In2Se3/Ga2S3 system is found to exhibit a conduction and a valence band offsets of values of 0.53 and 0.47 eV at the Ge/In2Se3 and of values of 0.30 and 0.70 eV at the In2Se3/Ga2S3 interfaces, respectively. The values are high enough to actualize quantum confinements in the heterojunction device. The formed double and three layers displayed higher light absorbability than single layers. On the other hand, the dielectric dispersion analysis has shown a wide tunability in the dielectric property in visible light and near IR regions. The dielectric responses at the Ge/In2Se3 and at the Ge/In2Se3/Ga2S3 interfaces are linear below 2.10 eV and 1.53 eV, respectively. The modeling of the dielectric function revealed the optical conductivity parameters presented by the drift mobility, scattering time, plasmon frequency and free electron density. It was observed that the quantum condiment at the Ge/In2Se3 interfaces improved both of the drift mobility and made the scattering time longer at femtosecond levels. The establishing of the second quantum confinement at the second interface In2Se3/Ga2S3 raised the drift mobility more and extended the scattering time further. With the estimated plasmon frequencies, the formation of the Ge/In2Se3/Ga2S3 interface appears to be promising for use in optoelectronic device production especially in photodetection issues.