Electron spin resonance measurements were performed on Er-doped and O co-doped material which had been prepared by means of metalorganic chemical vapor deposition. An isotropic line (with effective g-value of 5.95), which had already been reported, was observed in samples without O co-doping. In samples which were O co-doped, other strong anisotropic electron spin resonance lines which originated from 4 kinds of Er3+(4f11) center (A, B, C, D) were then observed in addition to the weaker isotropic line. The anisotropic g-tensors which were obtained by analyzing the angular dependence of the electron spin resonance lines indicated that the B and C centers had orthorhombic C2v symmetry. The A-center had a lower symmetry than orthorhombic, and the D center had trigonal C3i symmetry. The electron spin resonance intensities of the A, B and C centers were some 2 orders of magnitude higher than that of the isotropic line with g = 5.95. The electron spin resonance intensity of the D center was an order of magnitude lower than those of A, B and C. The Er concentration-dependence of the relative electron spin resonance intensities of these centers was investigated. This indicated that the electron spin resonance intensities of A and D increased with increasing Er concentration, and those of B and C saturated above an Er concentration of 1018/cm3. The electron spin resonance measurement under light illumination, as well as the Er concentration-dependence, suggested that the B-center, with C2v symmetry, corresponded to the predominant Er luminescent center under host photo-excitation.

Electron spin resonance of Er-oxygen complexes in GaAs grown by metalorganic chemical vapor deposition T.Ishiyama, E.Katayama, K.Murakami, K.Takahei, A.Taguchi: Journal of Applied Physics, 1998, 84[12], 6782-7