Microstructure of GaAs thin films grown on glass using Ge seed layers fabricated by aluminium induced crystallization

摘要

We perform the growth of GaAs epilayers by molecular beam epitaxy (MBE) on Ge pseudo-substrates obtained by the aluminium induced crystallisation (AIC) of thin amorphous Ge layers deposited on silica. Despite the apparent uniformity of the AIC-Ge layer, large domains (more than 50 mu m wide) previously thought to be monocrystalline are found to actually consist in smaller grains (500 to 1000 nm wide), separated by low angle grain boundaries. These defects are transferred during epitaxy to the GaAs layer and degrade the quality of the III-V material. In our growth conditions, the MBE results in the selective deposition of thin GaAs layers on Ge with respect to the silica support, but selectivity is progressively lost with increasing layer thickness.