Monolithic color-selective ultraviolet (266-315 nm) photodetector based on a wurtzite MgxZn1-xO film
A unique ultraviolet photodetector based on a metal-semiconductor-metal structure was fabricated from a wurtzite MgxZn1-xO film with gradually changing Mg content, homoepitaxially grown on a BeO-buffered ZnO substrate. The BeO layer filtered out the substrate photoresponse. The cutoff wavelength of the photodetector under zero bias was 266 nm with a UV/visible light rejection ratio of greater than 2 orders of magnitude in the deep UV region. Applying a bias, the cutoff wavelength exhibited a prominent continuous redshift from 266 (0 V) to 315 nm (3 V), indicating the capability for multi-band UV detection on a monolithic chip. The bias-controlled wavelength-selective UV photoresponse mechanism occurred in the optically active area in a compositionally distributed MgxZn1-xO alloy that was achieved by molecular epitaxial growth.