Low Vapor Pressure Organoarsenic Compounds as Alternatives to Arsine in GaAs MOVPE.

We have investigated methyl, ethyl and butyl-based organoarsenic compounds as alternatives to arsine in the metalorganic vapor phase epitaxy (MOVPE) of GaAs. These compounds are typically low vapor pressure liquids and thus much safer to handle than arsine, which is a toxic high pressure gas. To enable a direct comparison of the alkylarsine and arsine sources, measurements of their growth and thermal decomposition properties were obtained in the same reactor under identical conditions. Data are presented on the effects of precursor composition and purity on the electrical and optical properties of the films and their growth rates. The lowest quality films were obtained with the fully substituted alkylarsines, e.g., trimethylarsine and triethylarsine. Mono and di-substituted alkylarsines yielded films with improved surface morphology, lower carbon incorporation and higher electron mobilities. Best results were obtained with the butyl compound, monotertiarybutylarsine, in which only one of the hydrogen atoms of arsine is replaced by an organic group.