ESR study of GaAs : Er codoped with oxygen grown by organometallic vapor phase epitaxy

X-band ESR measurements of GaAs:Er grown at 543 degreesC by organometallic vapor phase epitaxy (OMVPE) with and without an additional O-2 flow (sample s I and II, respectively) have been performed at 3.5 K. Sample I shows an i sotropic ESR signal around g = 6 together with several anisotropic ESR sign als in the g-value region from 0.7 to 3, while sample II shows only an isot ropic ESR signal around g = 6, suggesting the formation of Er-2O centers in sample I. We also observed the temperature dependence of the anisotropic s ignals in sample I from 3.5 to 15 K. The integrated intensity showed a maxi mum at 7 K suggesting that these ESR signals are coming from the excited st ates very close to the ground state. The ESR signal also turned out to be v ery sensitive to the growth temperature of GaAs:Er. GaAs:Er grown at 628 de greesC by OMVPE with an additional O-2 flow (sample III) showed no ESR sign al at 3 K. These results will be discussed in connection with PL results of samples I-III. (C) 2001 Elsevier Science B.V. All rights reserved.