Bandgap engineering in CuO nanostructures: Dual-band, broadband, and UV-C photodetectors

In this work, the bandgap of CuO (p-type semiconductor) has been engineered from an indirect bandgap of similar to 1eV to a direct bandgap of 4eV just by tuning the nanostructure morphology and midgap defect states. The absorption in near-infrared (NIR) and visible regions is ordinarily suppressed by controlling the growth parameters. Considering the increasing scope and demand of varying spectral range (UV-C to NIR) photodetectors, the systematic variation of the available density of states (DOS) at a particular energy level in CuO nanostructures has been utilized to fabricate dual-band (250nm and 900nm), broadband (250nm-900nm), and UV-C (250nm) photodetectors. The sensitivity and detectivity of the photodetector for broadband detectors were similar to 10(3) and 2.24x10(11) Jones for the wavelengths of 900nm and 122 and 2.74x10(10) Jones for 250nm wavelength light, respectively. The UV-C detector showed a sensitivity of 1.8 and a detectivity of 4x10(9) Jones for 250nm wavelength light. A plausible mechanism for the photoconduction has been proposed for explaining the device operation and the effect of variation in available DOS. The obtained photodetectors are the potential candidates for future optoelectronic applications.