Metalorganic vapor phase epitaxy growth of ternary tetradymite Bi2Te3−xSex compounds

• Bi2Te3−xSex films over entire composition range are grown by MOCVD on sapphire substrates.
• The composition of thin films strongly depends on their thickness.
• AFM and X-ray studies confirmed high crystalline quality of the films.
• The composition Bi2Te2Se has the largest resistivity.

We report on a metal organic vapor epitaxy (MOVPE) of Bi2Te3−xSex films over the entire range of compositions (0≤x≤30≤x≤3) for the first time. The films were grown on Al2O3(0001) substrates at 465 °C using trimethylbismuth (Bi2Me3), diethyltellurium (Et2Te) and diisopropylselenium (iPro2Se) as metalorganic sources. To realize the 2D growth mode and to grow films with flat surfaces and high crystalline quality, a thin ZnTe buffer layer was used. As-grown films were studied using optical and AFM microscopy techniques and X-ray diffraction. It was found that under steady growth conditions the composition of Bi2Te3−xSex films strongly depends on the film thickness. But a high rate of interdiffusion of chalcogens at the growth temperature rapidly leads to a homogeneous composition of the film in the growth direction. Dependence of the intensity of X-ray reflection (0012) on the composition of Bi2Te3−xSex films x has extremes near x  =1 (Bi2Te2Se)(Bi2Te2Se) and x  =2 (Bi2Se2Te)(Bi2Se2Te). The AFM micrographs and profiles show large (above 2 μm) triangle-shaped atomically flat terraces with step height of a quintuple layer (0.90 nm) of the tetradymite-type compounds. The electronic properties of the grown films have been characterized via four probe magnetotransport measurements.