Electron spin resonance of Er–oxygen complexes in GaAs grown by metal organic chemical vapor deposition

Abstract

We have performed electron spin resonance (ESR) measurements on Er-doped GaAs grown with oxygen codoping by metal organic chemical vapor deposition. An isotropic line (an effective g value, g=5.95) which had been already reported was observed in samples without oxygen codoping. On the other hand, for samples with oxygen codoping other strong anisotropic ESR lines originated from four kinds of Er3+(4f11) centers (A, B, C, and D) were newly observed in addition to the weaker isotropic line. The anisotropic g tensors obtained by analyzing the angular dependence of the ESR lines indicate that B and C centers are of orthorhombic C2v symmetry, A center has lower symmetry than orthorhombic symmetry, and D center is of trigonal C3i symmetry. The ESR intensities of A, B, and C centers were approximately two orders of magnitude higher than that of the isotropic line with g=5.95. The ESR intensity of D center was one order of magnitude lower than those of A, B, and C. The Er concentration dependence of the relative ESR intensities of these centers was investigated, which indicates (i) the ESR intensities of A and D increase with increasing Er concentration, and (ii) those of B and C are saturated above the Er concentration [Er]⩾1018 cm−3. The ESR measurement under light illumination, as well as the Er concentration dependence, suggests that the B center with C2v symmetry corresponds to the dominant Er luminescent center under host photoexcitation.