EX-SITU ATOMIC-FORCE MICROSCOPY STUDIES OF VICINAL SURFACES GAAS(001)GROWN BY MOLECULAR-BEAM EPITAXY

The step periodicity of GaAs vicinal surfaces, grown by molecular beam epitaxy (MBE) was studied for a large range of misorientation (0.2 de grees to 2 degrees towards [111]) using ex-situ atomic force microscop y (AFM) under dry nitrogen gas. After growth, the statistical distribu tion of the terrace width and the correlation length along the steps w ere consistent with a thermodynamic equilibrium model taking into acco unt an AL(-2) step-step interaction. These observations are qualitativ ely similar to Si and metals after thermal annealing but, in addition to elastic interaction, the dipole-dipole contribution has to be consi dered in order to explain the large value of the coefficient A (A(Ga) = 1.5 eV Angstrom) deduced for the force coefficient between the galli um terminated steps. Step bunching occurred for highly Si-doped GaAs g rowth and we discuss the best method for carrying out the measurements in order to determine the step-step interaction.