Kinetics and crystal texture improvements on thin germanium layers obtained by aluminium induced crystallization using oxygen plasma

The fabrication of strongly-textured thin crystalline germanium layers on amorphous silica substrates can be achieved by aluminium induced crystallization using the 'aluminium induced layer exchange' mechanism. This requires a diffusion barrier, or interlayer, between the Al and Ge layers with a specific chemistry. We investigate here the effect of oxygen plasma on this interlayer as an alternative route to the standard air-exposure process. We find that the plasma treatment strongly slows down the kinetics of the crystallization. This can be compensated by a higher process temperature, after which the defect density becomes similar to that of air-oxidized but with defects of smaller size. This substantially improves the overall texture of the Ge layer and a near complete (111) orientation is obtained.