Origin of nitrogen-pair luminescence in GaAs studied by nitrogen atomic-layer-doping in MOVPE

Nitrogen atomic-layer-doping and nitrogen uniform doping were performed on (001) GaAs by metalorganic vapor phase epitaxy using dimethylhydrazine as a nitrogen doping source. Nitrogen doped GaAs layers showed several sharp photoluminescence lines relating to excitons bound to nitrogen pairs at 8 K. We investigated the origins of these sharp photoluminescence lines, that is, the distance between the nitrogen atoms of a pair and their pairing direction. The photoluminescence spectra for nitrogen atomic-layer-doped GaAs are different from those for uniformly nitrogen-doped GaAs, as expected from the different dimensions of the nitrogen atom distribution. To estimate the distance between the nitrogen atoms of a pair and their pairing direction, we performed double atomic-layer doping and varied the distance between the two atomic-layer-doped planes. When the two planes are brought to 1 nm of each other, lines observed only in uniformly doped GaAs appear. From this result, it was determined that the pairing directions corresponding to these lines are not included in the (001) plane and the corresponding distance between the nitrogen atoms of a pair is around 1 nm.