Growth of Tl-containing III-V materials by gas-source molecular beam epitaxy

The synthesis of the Tl-V binaries and In-Tl-V alloys have been investigated using gas-source molecular beam epitaxy. With this approach, neither the binary nor ternary Tl-containing phosphides could be attained, with virtually all of the Tl present in the form of metallic droplets. While the Tl-As system was found to produce a compound, this phase was Tl rich with a Tl/As ratio ranging between 6/1 to 9/1. This phase was always accompanied by metallic Tl which oxidized rapidly upon exposure to air. Zinc blende InTlAs was synthesized, as determined by Auger electron spectroscopy, but exhibited compositional variations believed to be due to severe Tl surface segregation. The formation of both the Tl-As and In-Tl-As phases was found to be strongly dependent upon growth temperature. The Tl-Sb system also produced a Tl rich phase, with a composition of Sb/sub 2/Tl/sub 7/, as measured by electron microprobe analysis. Unlike the arsenides and phosphides, the Tl-Sb compound could be synthesized even at growth temperatures of 375/spl deg/C. This phase was found to exist in a CsCl structure and was accompanied by metallic Sb rather than elemental Tl as for the arsenides.