Molecular beam epitaxy of high magnesium content single-phase wurzite MgxZn1-xO alloys (x ≃ 0.5) and their application to solar-blind region photodetectors

A series of single-phase wurzite MgxZn1-xO alloys from x = 0 to 0.5 were successfully obtained by molecular beam epitaxial growth on sapphire substrates, resulting in artificial tuning of band gap energy E-g from 3.3 to 4.5 eV which covers UV-A, UV-B, and solar-blind spectral regions. The problem of phase separation ever reported in the growth of MgxZn1-xO with higher Mg content, e.g., x > 0.4 and E-g > 3.9 eV, has been overcome by using a ZnO buffer layer. The Mg0.5Zn0.5O layers have been applied to a planar geometry Schottky type metal-semiconductor-metal photodetector, exhibiting the photoresponse for the wavelength shorter than 270 nm which correspond to the solar-blind region.