Hydrothermal Growth and Photoluminescence of Zn 1 - x Mg x O Alloy Crystals

Zn 1 - x Mg x O alloy formation via band gap engineering is important in the development of blue−UV optoelectronic devices by providing lattice-matched transparent substrates for ZnO and nitride-related devices. Zn 1 - x Mg x O alloy single crystals (Zn 0.97 Mg 0.03 O and Zn 0.945 Mg 0.055 O) have been successfully grown by the hydrothermal technique. The growth experiments were carried out at 650 °C and 15−18 kpsi in alkaline solutions. Zn 1 - x Mg x O alloy crystals were formed at pressures below ∼22 kpsi at the growth temperature of 650 °C. These conditions are similar to the formation of MgO under hydrothermal conditions. A thin ZnO layer formed on the surface of the ZnMgO crystals as the autoclaves cooled to room temperature. After the ZnO layer was removed by etching or polishing from both the Zn 0.97 Mg 0.03 O and Zn 0.945 Mg 0.055 O samples, blue shifts of the photoluminescence emission from the 3.364 eV line of pure ZnO to 3.414 and 3.447 eV, respectively, were measured at ∼18 K. The composition of the alloys was confirmed by using secondary ion mass spectroscopy (SIMS) elemental analysis. X-ray diffraction indicated that the alloy crystals have good structural quality, whereas the lattice parameters are smaller than those of pure ZnO (for Zn 0 . 945 Mg 0.055 O a = 3.2416 Å, c = 5.1998 Å) because the radius of Mg 2+ is smaller than that of Zn 2+ .