Corundum Ga2O3 – the up-and-coming wide bandgap semiconductor for future UV sensing

events hall

Chancellor’s Fellow Lecturer Dr. Fabien Massabuau

03.02.2022

ZOOM

14:30

Gallium oxide (Ga2O3) is a wide bandgap semiconductor of strong interest for future power electronics and ultraviolet (UV) optical applications. This compound exists under several phases, with the corundum α phase variant (α-Ga2O3) displaying several indisputable assets: (i) it exhibits the largest bandgap (5.3 eV) amongst all phases, (ii) is isostructural with several other semiconducting group-III or transition metal sesquioxides (e.g. In2O3, Ti2O3) and (iii) with the cheap and widely available sapphire (α-Al2O3) substrate.

This presentation will give an overview of the group’s activities on α-Ga2O3 on growth, characterization, bandgap engineering and applications for UV sensing.

We demonstrated that α-Ga2O3 can be synthesized using plasma-enhanced atomic layer deposition (ALD). The deposition temperature has a critical impact on the film crystallinity, with deposition temperatures below 200oC resulting in amorphous material, while temperatures between 250 and 350oC result in mainly α phase material, and films of mixed α and ε phases are obtained for temperatures above 350oC.

The effect of post-growth annealing conditions (temperatures and ambient) on the deposited film quality will also be discussed. The annealing temperature was found to have a strong influence on the film crystallinity, with 400oC leading to the optimal crystal quality. These films were then processed into photodetectors and tested under 240 nm UV illumination and 10 V bias. All the films exhibited solar-blind photodetection behavior, and a sharp 3-order of magnitude increase in device responsivity was obtained upon annealing.

Finally, we discuss the potential for bandgap engineering of α-Ga2O3 films using Ti. Crystalline α-(TixGa1-x)2O3 films can be produced with a composition up to x~5%, leading to a change of bandgap of ~ 200 meV.

Host: Asst. Prof. Yonatan Calahorra

Link to ZOOM