A mass spectrometric study of AsH(3) and PH(3) gas sources for molecular beam epitaxy.

The mass spectra of species resulting from the decomposition of AsH(3), PH(3) and a mixture of both have been studied with a modulated beam mass spectrometer. Two types of crackers, one that decomposes the hydrides at high pressure (~200 - 2000 Torr) and one that decomposes them on a Ta catalyst at low pressure (~0.1 Torr) were used. Operating conditions that yield predominantly dimers are readily achieved with both sources although a significant amount of monomer appears to be present in the flux from the low pressure source.