The migration of Si during the metal-organic vapor-phase epitaxial growth of laser structures was studied by means of secondary ion mass spectroscopy. The migration process was found to depend mainly upon the Si concentration in the AlGaAs layer; for both silane and disilane doping gases. Above a critical concentration of about 3 x 1018/cm3, Si migrated into the nominally undoped GaAs layer. This shift in the Si front became even more pronounced when the GaAs layer was grown at a lower rate than that of the AlGaAs layer. The Si depth profile had the same gradient as the Al depth profile; even in layers with a large shift of the Si front. Migration appeared to occur preferentially towards the growth front. It was concluded that the process was governed not only by diffusion, but also by surface kinetics. The effect of Si migration upon the threshold current density of broad-area lasers was significant only for a large shift of the Si front into the active GaAs layer.

Silicon Migration during MOVPE of AlGaAs/GaAs Laser Structures. E.Veuhoff, E.Baumeister, R.Treichler: Journal of Crystal Growth, 1988, 93[1-4], 650-5