Microscopic mechanisms behind the Al-induced crystallization of a-Ge:H films

Raman and infrared spectroscopies have been used to study the crystallization of sputtered hydrogenated amorphous germanium (a-Ge:H) films induced by variable amounts of aluminum. Under the selected deposition conditions Al induces the partial crystallization of Ge films deposited onto crystalline silicon substrates. The analysis of experimental data indicates that Al atoms play a key role in the process. The comparison with data on the local order and coordination of Ga atoms in a-Ge:H suggests that fourfold coordinated Al atoms sitting at the center of tetrahedral sites act as crystallization seeds.