Effect of growth parameters on MgxZn1−xO films grown by metalorganic chemical vapour deposition

MgxZn1−xO thin films have been successfully grown on Al2O3 (0 0 0 1) substrate by metalorganic chemical vapour deposition (MOCVD). The influences of Mg incorporation and growth parameters (temperature and VI/II ratio) on optical and structural properties are examined. The near band edge emission is shifted by 450 meV when the Mg content in the vapour is increased to 0.6. Scanning electron microscopy and X-ray diffraction results confirm the existence of phase segregation in MgxZn1−xO thin films. Growth at low temperature and high VI/II ratio decreases the Mg incorporation. Low temperature photoluminescence illustrates an increase in free-to-bound, defect related emission arising from stacking faults and dislocations. This also reveals strong alloy broadening effects related to Mg incorporation. The effects of various oxygen precursors (oxygen gas and tertiary butanol) have been investigated, showing no major difference in terms of Mg incorporation. The temperature dependent photoluminescence measurements on layers with low Mg concentration (x(v)=0.05 and 0.1) show that the main bound exciton peak exhibits an s-shaped temperature dependence, characteristic of localization in a disordered alloy.