codoped with oxygen grown by organometallic vapor phase epitaxy

X-band ESR measurements of View the MathML source grown at 543°C by organometallic vapor phase epitaxy (OMVPE) with and without an additional O2 flow (samples I and II, respectively) have been performed at View the MathML source. Sample I shows an isotropic ESR signal around g=6 together with several anisotropic ESR signals in the g-value region from 0.7 to 3, while sample II shows only an isotropic ESR signal around g=6, suggesting the formation of Er-2O centers in sample I. We also observed the temperature dependence of the anisotropic signals in sample I from 3.5 to View the MathML source. The integrated intensity showed a maximum at View the MathML source suggesting that these ESR signals are coming from the excited states very close to the ground state. The ESR signal also turned out to be very sensitive to the growth temperature of View the MathML source. View the MathML source grown at 628°C by OMVPE with an additional O2 flow (sample III) showed no ESR signal at View the MathML source. These results will be discussed in connection with PL results of samples I–III.