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

We report a study, based on high resolution X-ray diffraction and phot oluminescence (PL) measurements, of In segregation in InAs/GaAs quantu m wells (QWs) 1 monolayer thick, grown by molecular beam epitaxy (MBE) and atomic layer molecular beam epitaxy (ALMBE), at different tempera tures. The In content in the structures is evaluated by simulations of diffraction profiles, carried out according to the dynamical theory o f X-ray diffraction. To study the segregation, we propose a new approa ch based on a suitable choice of the diffraction geometry. This approa ch 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 va lue (6.5 Angstrom) is found in the ALMBE QWs grown at 460 degrees C. P L results on the same QWs can be interpreted in terms of a growth-temp erature-dependent segregation. Our results show that the effects of se gregation decrease with decreasing growth temperature and that, at a g iven temperature, segregation is more effective in the ALMBE structure s than in the MBE counterparts.