Realization of cubic ZnMgO photodetectors for UVB applications

Cubic ZnMgO (c-ZnMgO) with a band gap in the ultraviolet-B (UVB) region was deposited for the first time on the a-face sapphire substrate by molecular beam epitaxy using a thin low-Zn-content ZnMgO film as the buffer layer. The metal-semiconductor-metal photodetectors were demonstrated on this c-ZnMgO with different finger gaps, and their cut-off wavelength is around 320 nm. At 10 V, the device with a finger gap of 2 mu m shows a low dark current of 3 pA, and its peak responsivity at 302 nm is similar to 5.188 A W-1. A further temporal photoresponse study reveals that the c-ZnMgO UVB photodetectors display a fast response speed (90-10% decay time is around 24 mu s) with good reproducibility and stability. Our findings indicate that the present c-ZnMgO UVB photodetectors are very promising for future optoelectronic device applications.