Comparison Study of β-Ga2O3 Photodetectors Grown on Sapphire at Different Oxygen Pressures

In this paper, β-Ga<sub>2</sub>O<sub>3</sub> ultraviolet photodetectors were grown on sapphire utilizing the laser molecular beam epitaxy tool. The impact of oxygen pressure <italic>P</italic><sub>O2</sub> in growth chamber on the crystal quality, the surface morphology, the chemical component of Ga<sub>2</sub>O<sub>3</sub> films, and the electrical performance of photodetectors are characterized. As the <italic>P</italic><sub>O2</sub> is increased during growth, the concentration of oxygen vacancy (<italic>V</italic><sub>O</sub>) is effectively reduced. The photodetector grown at the <italic>P</italic><sub>O2</sub> of 0.05 mbar exhibits the significantly improved photocurrent <inline-formula><tex-math notation="LaTeX">$I_{{\rm{photo}}}$</tex-math></inline-formula> and responsivity <italic>R </italic> characteristics in comparison with the device grown with the <italic>P</italic><sub>O2</sub> of 0.01 mbar, which is attributed to a reduction in the number of <italic>V</italic><sub>O</sub>. However, as the <italic>P</italic> <sub>O2</sub> continuously increased to 0.09 mbar, <inline-formula><tex-math notation="LaTeX">$I_{{\rm{photo}}}$ </tex-math></inline-formula> and <italic>R</italic> of the detector are degraded, which might be due to the fact that the gallium vacancies (<inline-formula><tex-math notation="LaTeX">$V_{{\rm{Ga}}}$</tex-math></inline-formula>), as the dominant trapping centers, lead to the recombination of photo-generated carriers.

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