Functional Properties and Band Gap Engineering of ZnO-GaN Alloys

Abstract

Renewable energy sources play a vital role in handling the increasing energy demand, as well as the aim to reduce carbon emissions. New materials for solar cell applications are being developed for this sole reason. The ZnO-GaN (ZOGN) semiconductor alloys, consisting of two industrial well-proven materials with intriguing optical properties, have been found to yield tunable absorption from UV- and well in to the visible part of the solar spectrum, due to the so-called band bowing effect. The alloys have been developed and utilized for hydrogen production through overall water-splitting, and also show promising properties for optoelectronics. In this work, the fundamental properties of ZOGN alloys have been investigated with the aim of utilization in applications as solar cells, photo detectors and photo diodes. Highly crystalline alloy thin films, grown using magnetron sputtering, have been investigated in terms of structural, optical and electrical properties. In particular, the mechanisms governing the band bowing effect observed in the materials have been explored, in order to understand and control the tunable absorption. This control is highly relevant for applications as solar cells, photo diodes and overall water-splitting.