Planar Hybrid UV-C Photodetectors Based on Aerosol-Jet Printed PEDOT:PSS on Different Ga2O3 Thin Films

Ultra-wide bandgap semiconductors like Ga2O3, presenting intrinsic spectral selectivity in the UV-C region of the electromagnetic spectrum, are especially well suited for application as solar-blind photodetectors. In this work, photodiodes based on a planar hybrid heterojunction between Ga2O3 and an organic semiconductor are fabricated. Specifically, the photodetectors consist of layers of nominally undoped β-Ga2O3, κ-Ga2O3, amorphous Ga2O3 or Si-doped κ-Ga2O3 over which an ink based on heavily doped PEDOT:PSS is directly deposited by Aerosol-Jet Printing. Optimization of the latter process is pursued, ensuring the minimization of overspray and ill-defined features over all the tested layers, especially on the amorphous one, which was found to be the most compatible with this deposition technique. After characterization of the fabricated devices electrical and optoelectronic properties, β-Ga2O3 presents the best lower-bound estimate values of peak responsivity, external quantum efficiency, and a specific detectivity of 4.5∙10-2 A/W, 23% and 3.2∙1012 Jones respectively, at a wavelength (λ) of 240 nm, along with a UV-C / visible (λ = 240 / 400 nm) rejection ratio of 1.6·103. However, as the sputtering deposition process is scalable and inexpensive compared to epitaxial crystal growth, amorphous Ga2O3 emerges as a cost-effective alternative to β-Ga2O3 for solar-blind photodetection.