Co-deposition of band-gap tuned Zn1-xMgxO using high impulse power- and dc-magnetron sputtering

High impulse power- and direct current- magnetron sputtering have been used to reactively co-deposit Zn1-xMgxO onto a 100 mm diameter a-plane sapphire wafer at 200 C. The Zn1-xMgxO film exhibited low surface roughness, high transparency, high electrical resistivity and a Mg fraction (x) depending on substrate location. The optical bandgap of the film varied monotonically with x up to the miscibility limit of ∼0.32, beyond which a mixed cubic/wurtzite structure formed. Annealing at 550 C in forming gas (95% N2, 5% H2), caused reduced compressive stress and dramatically reduced electrical resistivity. The latter was attributed to shallow doping by hydrogen bound to oxygen vacancies and these changes occurred in the wurtzite Zn1-xMgxO without detectable phase transformation. A filtered UV detector, with active and filter layers fabricated from the co-deposited film, exhibited sensitivity to UV in a 330-355 nm pass-band and approximately three orders of magnitude UV-to-visible rejection.