Because of the extreme toxicity ofA3, it is highly desirable to employ gaseous As sources which contain fewer As-H bonds. Attempts to introduce compounds such as tertiarybutylarsine (TBAs) during growth by metal-organic molecular beam epitaxy (MOMBE) have been somewhat unsuccessful due to the need for pre-cracking of these materials, and to the extreme reactivity of the hydrocarbon radicals released upon their decomposition. These byproducts have been found to severely degrade various components in the growth system, and could lead to enhanced carbon uptake at low growth temperatures. Phenylarsine (PhAs) offers several advantages over the more common As substitutes as it has been demonstrated to decompose at growth temperatures of ≥575°C, and the byproducts of its decomposition are expected to be far less reactive than the byproducts of the other As precursors.
In this paper we will discuss the growth of GaAs and AlGaAs at low growth temperatures (≤530°C) using PhAs as the As source. In this temperature range, the III-V growth rate is restricted due to the cracking efficiency of the PhAs. For example, at 530°C, a PhAs flow rate of ∼5.4 seem limits the growth rate to ∼95 Å/ min while a similar flow of AsH3 through a low pressure cracker allows for deposition at rates >250 Å/min. Further comparisons of the two As sources will be discussed regarding their effect on GaAs and AlGaAs growth rates from triethylgallium, trimethylgallium, and trimethylamine alane, and their effect on carbon and oxygen impurity incorporation.