Growth of high-quality Bi₂Se₃ topological insulators using (Bi_1-xIn_x)₂Se₃ buffer layers

In this article, the authors first report on the optimum growth parameters for (Bi_1-xIn_x)₂Se₃ alloys of arbitrary composition using molecular beam epitaxy. It is found that smooth, single-phase films can only be obtained by using a sequential growth and annealing method to seed the film, after which normal codeposition growth can be used. The topological insulator Bi₂Se₃ is then grown on top of various (Bi_1-xIn_x)₂Se₃ buffers and the electrical properties measured. For Bi₂Se₃ films grown on high-quality buffer layers, the mobility is greatly enhanced and the carrier density reduced compared to growth directly on sapphire substrates, indicating a significant improvement in film quality. The use of an almost lattice-matched trivially insulating buffer layer is therefore crucial to the growth of high-quality topological insulators on arbitrary substrates.