We have measured micro-photoluminescence (PL) spectra of nitrogen delta (delta)-doped GaAs with various concentrations. In nitrogen delta-doped GaAs with low concentrations, the micro-PL spectra measured at different positions were individually different. In contrast, almost the same spectra were obtained for nitrogen delta-doped GaAs with higher concentrations and uniformly nitrogen-doped GaAs. The micro-PL study shows that there are no more than a few isoelectronic traps within a diameter of similar to 1 mu m. This indicates a good prospect for applications of isoelectronic traps to single photon emitting devices. (c) 2006 Elsevier B.V. All rights reserved.