Optimizing Gallium Oxide Thin Films for Electro-Optical Applications

Gallium Oxide is a wide-bandgap semiconductor which has shown great promise in recent years due to its distinctive opto-electrical properties. Its refractive index and ultra-wide bandgap can be tuned, and it has a very high breakdown field, making it a promising candidate for a wide range of applications, such as deep-UV photodetectors, low-loss optical waveguides or even transparent solar cells. Among possible deposition techniques, RF-Sputtering stands out for its ability to produce thin films with high quality and at a low cost.

In this work, the SentiFET deposition chamber was operationalised, and a furnace to enable high-temperature deposition was designed and built. Then, an exhaustive study was done on the influence of different parameters, such as deposition pressure and power, post-growth annealing temperature and duration and substrate used, on the optical and electrical properties of Ga2O3 thin films deposited by RF-Sputtering.

These samples were then fully characterized through complementary techniques such as profilometry, ellipsometry, optical transmission, Rutherford backscattering spectrometry, X-ray diffraction, atomic force microscopy and Raman spectroscopy, in order to determine their optical and structural properties, composition and surface roughness. To optimise the films' optical and electrical properties even further, the effect of doping via ion implantation with tin (Sn) was also investigated.

Finally, planar photodetectors with interdigitated contacts were fabricated based on these films, through photolithography, which were then evaluated in terms of their optical responsivity.