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 Mg x Zn 1- x O 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 Mg x Zn 1- x O 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 Mg 0.5 Zn 0.5 O 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.