  In situ Eu-doped {ZnCdO/ZnO}30 multilayer systems were grown on p-type
Si-substrates and on quartz substrates by plasma-assisted molecular beam
epitaxy. Various Eu concentrations in the samples were achieved by controlling
temperature of the europium effusion cell. The properties of as-grown and
annealed {ZnCdO/ZnO}30:Eu multilayers were investigated using secondary ion
mass spectrometry (SIMS) and X-ray diffraction methods. SIMS measurements
showed that annealing at 700{\deg}C and 900{\deg}C practically did not change
the Eu concentration and the rare earth depth profiles are uniform. It was
found that the band gap depends on the concentration of Eu and it was changed
by rapid thermal annealing. Varshni and Bose-Einstein equations were used to
describe the temperature dependence of the band gap of {ZnCdO/ZnO}30:Eu
multilayer structures and Debye and Einstein temperatures were obtained.
