PREPARATION BY MOLECULAR-BEAM EPITAXY AND ATOMIC LAYER MOLECULAR-BEAM EPITAXY AND CHARACTERIZATION OF INAS LAYERS 1-MONOLAYER THICK IN GAAS-BASED STRUCTURES

We report a study, based on high resolution X-ray diffraction and photoluminescence (PL) measurements, of In segregation in InAs/GaAs quantum wells (QWs) 1 monolayer thick, grown by molecular beam epitaxy (MBE) and atomic layer molecular beam epitaxy (ALMBE), at different temperatures. The In content in the structures is evaluated by simulations of diffraction profiles, carried out according to the dynamical theory of X-ray diffraction. To study the segregation, we propose a new approach based on a suitable choice of the diffraction geometry. This approach allows us to deduce a value of 5.5 Angstrom for the In segregation length in MBE structures prepared at 480 and 420 degrees C, and in the ALMBE structure prepared at 360 degrees C, while a slightly larger value (6.5 Angstrom) is found in the ALMBE QWs grown at 460 degrees C. PL results on the same QWs can be interpreted in terms of a growth-temperature-dependent segregation. Our results show that the effects of segregation decrease with decreasing growth temperature and that, at a given temperature, segregation is more effective in the ALMBE structures than in the MBE counterparts.