Multiple Exciton Generation in 3D-Ordered Networks of Ge Quantum Wires in Alumina Matrix

Abstract

Thin films containing 3D-ordered semiconductor quantum wires offer a great tool to improve the properties of photosensitive devices. In the present work, we investigate the photo-generated current in thin films consisting of an interconnected 3D-ordered network of Ge quantum wires in an alumina matrix. The films are prepared using nitrogen-assisted magnetron sputtering co-deposition of Ge and Al2O3. We demonstrate a strong photocurrent generation in the films, much stronger than in similar films containing Ge quantum dots. The enhanced photocurrent generation is the consequence of the multiple exciton generation and the films’ specific structure that allows for efficient carrier transport. Thin film with the largest nitrogen content showed enhanced performance compared to other thin films with 1.6 excitons created after absorption of a single photon at an energy nearly equal to the double bandgap value. The bandgap value depends on the geometrical properties of the quantum wires, and it is close to the maximum of the solar irradiance in this case. In addition, we show that the multiple exciton generation is the most pronounced at the photon energy values equal to multiple values of the thin film bandgap.