Structural and optical properties of thin InGaAsN insertions in GaAs, grown
by molecular beam epitaxy using an RF nitrogen plasma source, have been in
vestigated. Nitrogen incorporation into InGaAs results in a remarkable broa
dening of the luminescence spectrum as compared with that of InGaAs layer w
ith the same indium content. Correspondingly, a pronounced corrugation of t
he upper interface and the formation of well defined nanodomains are reveal
ed in cross-sectional and plan-view transmission electron microscope (TEM)
images, respectively. Raising the indium concentration in InGaAsN (N < 1 %)
to 35 % results in the formation of well defined separated three-dimension
al (3D) islands. The size of the nanodomains proves that the InGaAsN insert
ions in GaAs should be regarded as quantum dot structures even in the case
of relatively small indium concentrations (25 %) and layer thicknesses (7 n
m), which are below the values required for a 2D-3D transition to occur in
InGaAs/GaAs growth. Dislocation loops have been found in TEM images of the
structures emitting at 1.3 <mu>m. They are expected to be responsible for t
he degradation of the luminescence intensity of such structures in agreemen
t with the case of long-wavelength InGaAs-GaAs quantum dots.