Electrical resistivity and structural changes in amorphous Ge_1-xAl_x thin films under thermal annealing

This study correlates the structure and the resistivity changes that occur upon annealing in Ge1-xAlx thin films in the aluminum-rich range of compositions (centered in the eutectic x = 0.70). In all cases, the as-deposited films have a negative temperature coefficient of resistivity (TCR) and the structure is that of an amorphous Ge-Al network with some aluminum crystallites for x = 0.70 and x = 0.81. A large and irreversible decrease in the resistivity is observed upon annealing and is related to the increase in the aluminum crystallite density, which grows to the point where the film contains a continuous network of metallic crystallites. Crystallized films present a metallic behavior (positive TCR and low resistivity values). An anomalous resistivity minimum is observed for x = 0.59 and is related to the growth of aluminum textured crystals. © 1988.