Structural properties and thermal stability of CdZnO/ZnO heterostructures grown on sapphire substrate by metal-organic vapor phase epitaxy were studied. Zn/Cd interdiffusion and Cd evaporation appeared as key factors limiting the thermal stability of CdZnO/ZnO heterostructures. Cd diffusion in MOVPE ZnO was found to start already at 600C with an activation energy of ∼2.2eV and yielded a saturation in the Cd concentration at 0.1 to 1at%. The actual Cd content remaining in the samples upon annealing was determined by a competition between Cd evaporation via the surface and diffusion/segregation in the bulk.

Cd Diffusion and Thermal Stability of CdZnO/ZnO Heterostructures. Azarov, A.Y., Zhang, T.C., Svensson, B.G., Kuznetsov, A.Y.: Applied Physics Letters, 2011, 99[11], 1903-5