Growth of GaNxAs1-x atomic monolayers and their insertion in the vicinity of GaInAs quantum wells

The deposition of N-rich GaNAs atomic monolayers was investigated. Such layers were successfully grown while exposing a GaAs surface to a nitrogen plasma source during a growth interruption at 400degreesC in a molecular beam epitaxy reactor. N accumulation was confirmed and evaluated by secondary ion mass spectroscopy. This process is compatible with regrowth, as in situ monitored by reflection high-energy electron diffraction. The crystal shows good structural quality, as displayed by transmission electron microscopy, that reveals that the accumulation occurred within 1 nm. In a series of samples, two of these ultrathin GaNAs layers were inserted in GaAs barriers, on each side of a GaInAs quantum well (QW). A drastic effect of the N-rich layers on the QW photoluminescence (PL) intensity was observed, as well as on the carrier recombination dynamics, with a strong influence of the spacer thickness between the QW and the N-rich layers. A time-resolved PL analysis of these samples evidenced nonradiative relaxation times in the range of a few ps. This very short carrier lifetime is attributed to the presence of nonradiative centres related to the N-rich layers close to the QW, and can be used to design ultrafast optical devices.