Tuning the responsivity of monoclinic solar-blind photodetectors grown by metal organic chemical vapor deposition

Abstract

We report on the fabrication and characterization of solar-blind photodetectors based on metal organic chemical vapor deposition grown polycrystalline monoclinic indium gallium oxide alloys on sapphire using N2O for oxidation. The effects of growth conditions on indium incorporation efficiency and oxygen vacancies of the alloy, photo-to-dark current ratio (PDR), gain and responsivity of the fabricated photodetectors were investigated. The optical bandgap of the films was found to decrease due to the indium incorporation (x = 20.3%, 17.7%, 10.6% for samples A, B, and C, respectively) into the lattice of gallium oxide. By increasing the indium content incorporated into the lattice of , we demonstrated solar-blind photodetectors whose peak responsivity increased from 0.79 A/W () to 319.1 A/W, 66.1 A/W and 27.7 A/W for samples A, B and C, respectively at 5 V applied bias with the cut off wavelength below 280 nm. Increasing in content resulted in a higher concentration of oxygen vacancies in as-grown films. Increased oxygen vacancies as a result of the change in growth conditions lead to higher photoconductive gain, higher responsivities, and lower PDR, demonstrating a trade-off between responsivity and the PDR. To the best of our knowledge, the peak responsivity value reported in this work is the highest for based solar-blind photodetectors. Fast rise and fall times in the order of 100 ms have been measured for the photodetectors.