High performance, self-powered and thermally stable 200–750 nm spectral responsive gallium nitride (GaN) based broadband photodetectors

Abstract

We have developed and first reported Au/Ni/Pr2O3/GaN broadband photodetector device with photoresponsivity from 205 nm to 750 nm under self-powered mode. Using the Tauc's plot, the direct optical bandgap was found to be 4.8, 2.45 and 2.35 eV for the as-deposited, 550 °C and 650 °C post annealed samples, respectively. XRD study revealed that the phase of the as-deposited and post-annealed Pr2O3 films on GaN was monoclinic in nature. Atomic force microscopy method was engaged in non-contact mode to investigate the surface morphology of Pr2O3 films on GaN and the rms surface roughness was improved for the 650 °C post-annealed sample as 1.1 nm compared to other samples. In XPS study, two main Pr3d well separated XPS peaks were noticed at 933.5 eV (m) and 953.9 eV (m′) which corresponds to spin-orbit doublets of 3d5/2 and 3d3/2, respectively. In addition, the transient response measurements of the fabricated 650 °C post annealed device confirmed good stability even for the applied bias voltage of 20 V in the entire UV region. Further, the 650 °C post annealed device at 20 V provided best rise and fall times of 0.57 s and 0.41 s at 360 nm, respectively. The responsivity of the fabricated BB PD device at 650 °C revealed the evidence of bias dependency because of photoconductive gain. The attained progress in the fabricated PD device performance was due to the improved light absorption as evidenced from the optical absorption study. This results the transport of photogenerated electron-hole pairs across the bandgap by limiting recombination/trap states and intentionally deposited LT GaN buffer layer at the interface of sapphire/GaN. These results suggest that the developed BB PD device could also have the potential usage in optoelectronic device applications.