Analysis of GaAs MOMBE Reactions by Mass Spectrometry

Abstract
The thermal decomposition of trimethylgallium (TMG) under metal-organic molecular beam epitaxy (MOMBE) conditions is studied by mass spectrometry. For the first time, it is observed that the amount of Ga-containing species desorbed from the GaAs surface decreases above 350°C. Measurements on CH3, CH4 and C2H6 indicate that TMG pyrolyzes by releasing methyl radicals. The amount of Ga-containing species desorbed from the SiO2 surface does not show a steep decrease up to 530°C, which indicates that no thermal decomposition occurs on SiO2. This explains the mechanism of selective epitaxy in MOMBE.