Diffusion of Mn in gallium arsenide

Abstract

The aim of this work is to compare diffusion coefficient and shape of the manganese atomic profile in GaAs treated under different annealing conditions. Diffusion was performed from implanted Mn as well as from external source of Mn. Manganese implanted GaAs, GaAs:Zn and GaAs:Te bulk samples were investigated. Implantation was performed at room temperature to a dose of 10 16/cm 2 at an energy of 150 keV. The samples, were protected with AlN layers, and annealed at 800 °C with RTA (rapid thermal annealing) method as well as at 700 and 900 °C in a sealed quartz ampoule. After removing the AlN films the extent of diffusion of the species was characterized using the secondary ion mass spectrometry (SIMS) technique. The depth profiles of in-diffused manganese in RTA experiment strongly indicate that the diffusion coefficient D is concentration-dependent. For both: quartz ampoule and RTA annealings of implanted samples, the Mn diffusivity was found larger when GaAs was annealed with the AlN cap than that annealed without a cap. Over 10 times shallower diffusion range in uncovered samples than those encapsulated with AlN is interpreted in terms of generation of additional vacancies in the Ga sub-lattice. Mn atoms incorporate in Ga sites lowering thus the diffusion coefficient. In case of diffusion from external source into differently doped GaAs, the largest diffusion coefficient was found for GaAs:Zn. This result indicates highest Mn diffusivity in the sample with a low Fermi level which provides lowest concentration of ionized Ga vacancies. Both results confirm an interstitial diffusion mechanism and decreasing diffusion coefficient with increasing gallium vacancy concentration. The Boltzmann–Matano analysis was employed to evaluate the concentration-dependent diffusion coefficient of Mn in GaAs.