Vertically Oriented Topological Insulator Bi₂Se₃ Nanoplates on Silicon for Broadband Photodetection

As an exotic state of quantum matter, topological insulators like Bi2Se3 have potential applications in low power electronic and optoelectronic devices. Bi2Se3 nanoflakes or films with (001) orientation, laying horizontally on substrates, have been studied extensively in the past few years. Here we report the growth and photodetection response of Bi2Se3 nanoplates oriented vertically on the p-type Si substrate. This unconventional structure and geometry provide a higher effective absorption length for light absorption and potentially more efficient photocarrier transport via the topologically protected surface states or the basal plane of Bi2Se3 nanoplates. By compensating Bi2Se3 native defects with Cu doping, we achieve an increase of 42 times in the photocurrent when the Cu concentration is 3.87 at. %. Our work paves a way for exploring the excellent optoelectronic properties of topological insulator films with an unconventional orientation.