Donor passivation in n-AlInAs layers by fluorine

The origin and mechanism for the thermal degradation of the n-AlInAs layer are discussed. The thermal degradation of carrier concentration and mobility is found to occur predominantly in the n-AlInAs layer, which is caused by annealing at a temperature less than 450/spl deg/C. The origin of the deterioration is ascertained to be the thermally diffused fluorine, which passivates donors in the n-AlInAs layer. As the electronegativity of the fluorine atom is the largest among the elements, and the atomic radius of fluorine atom is considerably small enough to pass through the crystal, fluorine atoms are reasonably thought to diffuse into the n-AlInAs layer then react with the free electrons, which results in the F/sup -/ scattering centers (F/sup -/: ionized fluorine).