Optical properties of mist CVD grown $\alpha$-Ga$_2$O$_3$

TL;DR

This study investigates the optical properties of mist CVD grown alpha-Ga2O3, revealing excitonic absorption, band transitions, and high-performance UV photodetectors with notable responsivity and rejection ratio.

Contribution

It provides new insights into the excitonic and band transition properties of mist CVD grown alpha-Ga2O3 and demonstrates effective UV photodetectors fabricated on this material.

Findings

Excitonic absorption observed at 5.3 eV

Spectral responsivity shows a sharp band edge at 230 nm

Photodetectors achieved 1 A/W responsivity and 100 UV-visible rejection ratio

Abstract

We report on the study of optical properties of mist CVD grown alpha Gallium oxide with the observation of excitonic absorption in spectral responsivity measurements. 163 nm of Gallium oxide was grown on sapphire using Gallium acetylacetonate as the starting solution at a substrate temperature of 450 deg C. The film was found to be crystalline and of alpha phase with an on axis full width at half maximum of 92 arcsec as confirmed from X ray diffraction scans. The Taucs plot extracted from absorption spectroscopy exhibited two transitions in the UV regime at 5.3 eV and 5.6 eV, corresponding to excitonic absorption and direct band to band transition respectively. The binding energy of exciton was extracted to be 114 meV from spectral responsivity measurements. Further, metal semiconductor metal photodetectors with lateral inter digitated geometry were fabricated on the film. A sharp band edge was observed at 230 nm in the spectral response with peak responsivity of around 1 Amperes per Watt at a bias of 20 V. The UV to visible rejection ratio was found to be around 100 while the dark current was measured to be around 0.1 nA.