Mechanism of gallium arsenide MOCVD

Abstract

There are many points to be elucidated as to the chemical reactions between TMG and AsH 3. We have examined the vapor species in a MOCVD reactor by means of ir absorption spectroscopy and mass spectroscopy. The gas phase reaction of TMG with H 2 occurs above 400°C, giving rise to Ga deposition and CH 4 generation. On the other hand, the pyrolitic reaction of TMG takes place above 600°C in the absence of H 2, leading to Ga deposition and the generation of CH 4, C 2H 4, etc. In the mixture of TMG and AsH 3, an unidentified species which corresponds to 2080 cm −1 absorption spectrum is detected. Mass spectroscopic analysis reveals that a complex of the 2080 cm −1 spectrum is AsH(CH 3) 2 or AsH 2CH 3. In the case of AsH 3, AsH 3 decomposes catalytically on the surfaces of GaAs crystals. The dependence of the decomposition rate on the orientation of the GaAs surface and the Ga melt has been studied. The catalytic effect is largest on the (111)A surface and decreased in the order of the Ga melt and the (100) surface. The catalytic effect is not observed on the (111)B surface. Namely, the catalytic reaction rates depend on the density of Ga-single bonds. It is likely that the final species adhered to the (111)A at the largest rate in MOCVD is GaAs.