Photoresponse of n-ZnO∕p-SiC heterojunction diodes grown by plasma-assisted molecular-beam epitaxy

High quality n-ZnO films on commercial p-type 6H–SiC substrates have been grown by plasma-assisted molecular-beam epitaxy, and n-ZnO∕p-SiC heterojunction mesa structures have been fabricated. Current-voltage characteristics of the structures had a very good rectifying diode-like behavior with a leakage current less than 2×10−4A∕cm2 at −10V, a breakdown voltage greater than 20V, a forward turn on voltage of ∼5V, and a forward current of ∼2A∕cm2 at 8V. Photosensitivity of the diodes was studied at room temperature and a photoresponsivity of as high as 0.045A∕W at −7.5V reverse bias was observed for photon energies higher than 3.0eV.