Unraveling the infrared detection properties of Bi ₂ Te ₃ depending on thickness under the semiconductor and metal surface states

Bi₂Te₃ recently emerges as a promising candidate material for the next generation of mid-wave to long-wave infrared photodetection owing to its exceptionally narrow bandgap (approximately 0.2 eV) and the favorable photoelectronic properties. In particular, its topological insulator structure is safeguarded by time-reversal symmetry, leading to electronic structures with distinct surface and bulk states as well as distinctive optoelectronic properties. This study examines the infrared detection mechanism of Bi₂Te₃ across various thicknesses, aiming to elucidate the transport behavior and characteristics of internal carriers in Bi₂Te₃ under the complex interplay between the bulk state and surface states. Bi₂Te₃ films at various thicknesses were synthesized pulsed laser deposition with varied number of pulses which determines the actual thickness. The bandgap and the photoelectric response mechanism of Bi₂Te₃ at different layer thicknesses were investigated, and the charge carrier transport dynamics across layers were clarified. To summarize, this study offers a theoretical basis for advancing photoelectric detection devices designed to regulate Bi₂Te₃ at distinct thicknesses.