Effects of Post Annealing on Electrical Performance of Polycrystalline Ga2O3 Photodetector on Sapphire

Abstract

Effects of post annealing on the physical and electrical properties of solar-blind polycrystalline gallium oxide (Ga 2 O 3) ultraviolet photodetectors on the sapphire substrate are investigated. The grain size of poly-Ga 2 O 3 becomes larger with the post annealing temperature (PAT) increasing from 800°C to 1000°C, but it gets smaller with further raising PAT to 1100°C. A blue shift is observed at the absorption edge of the transmittance spectra of Ga 2 O 3 on sapphire as increasing PAT, due to the incorporation of Al from the sapphire substrate into Ga 2 O 3 to form (Al x Ga 1-x) 2 O 3. The high-resolution X-ray diffraction and transmittance spectra measurement indicate that the substitutional Al composition and bandgap of (Al x Ga 1-x) 2 O 3 annealed at 1100°C can be above 0.30 and 5.10 eV, respectively. The R max of the sample annealed at 1000°C increases about 500% compared to the as-deposited device, and the sample annealed at 1000°C has short rise time and decay time of 0.148 s and 0.067 s, respectively. This work may pave a way for the fabrication of poly-Ga 2 O 3 ultraviolet photodetector and find a method to improve responsivity and speed of response.

A Strategic Review on Gallium Oxide Based Deep‐Ultraviolet Photodetectors: Recent Progress and Future Prospects

“…A similar incorporation of Al atoms was observed by Hu et al. [ 133 ] in their photoconductive device after annealing above 1000 °C. The annealed device (at 1000 °C) showed a 500% jump in responsivity as compared to the as‐deposited polycrystalline β‐Ga 2 O 3 .…”

“…However, upon increasing the heat-treatment temperature to 900 °C, the peak in spectral response shifted towards shorter wavelengths owing to the diffusion of Al from the sapphire substrate. A similar incorporation of Al atoms was observed by Hu et al [133] in their photoconductive device after annealing above 1000 °C. The annealed device (at 1000 °C) showed a 500% jump in responsivity as compared to the asdeposited polycrystalline β-Ga 2 O 3 .…”

“…[158,232] However, it should be mentioned that on some substrates, particularly sapphire, thermal treatments above 1000 °C has shown to diffuse the substrate atoms (Al) into gallium oxide changing its bandgap and hence the spectral response. [133] Also for devices employing the use of metastable Gallia phases, excessive temperature may prove counter-productive by turning the metastable phase into β-Ga 2 O 3 . It has been reported by Hou et al that the record low dark current of 81 pA in their α-phase dominated gallium oxide based PD is because of the high quality of the grown films.…”

Postannealed (GaIn)2O3 Films Deposited by Sputtering for Ultraviolet Photodetection

“…The descending of responsivity with increasing annealing temperature should concern with the decreasing of oxygen vacancies. The oxygen vacancies can increase the response time by acting as electron traps in Ga 2 O 3 . , …”

“…The oxygen vacancies can increase the response time by acting as electron traps in Ga 2 O 3 . 19,28 Table 1 summarizes the characteristic parameters of our β-(GaIn) 2 O 3 film-based photodetector and the other recently reported (GaIn) 2 O 3 film-based photodetectors. The performance of our devices is comparable with that fabricated by the microwave irradiation method, and our devices showed improved photoproperties compared with devices fabricated by the cosputtering method.…”