Extremely sharp photoluminescence lines from nitrogen atomic-layer-doped AlGaAs/GaAs single quantum wells

We have applied nitrogen atomic-layer-doping to AlGaAs/GaAs single quantum wells. The atomic-layer-doping was performed at the center of the GaAs quantum well. The resulting structures show sharp photoluminescence lines with a full width at half maximum of 0.3 meV at 8 K. These lines are observed at longer wavelength than those obtained for undoped single quantum wells, indicating that they correspond to the excitons bound to nitrogen atoms in the quantum wells. The full width at half maximum of these nitrogen-related lines depends on the quantum well width. The lines remain sharp above a well width of 10 nm, while they become broad at 5 nm. This suggests that the diameter of the exciton bound to N atoms is about 10 nm. Furthermore, the binding energy of the excitons increases with increasing substrate temperature during the atomic-layer-doping.