The effect of deposition rate on the growth of epitaxial Ge on GaAs (100)

The role of deposition rate in the growth of Ge films on GaAs (100) was investigated using a new supersonic free-jet growth technique capable of achieving epitaxial growth rates several orders of magnitude higher than were previously available. The high growth rates are due to two factors: (1) the high arrival rate of digermane source molecules at a heated GaAs surface, and (2) the high thermal decomposition rate of digermane. Dramatic improvements in surface smoothness were observed with increasing deposition rate, while keeping all other deposition parameters fixed. When the arrival rate of digermane molecules was too high, amorphous films were deposited, in agreement with kinetic considerations. The supersonic free-jet growth technique and the microstructural and electrical properties of the resulting Ge films are described.