Transient photoconductivity and photoexcited carrier dynamics in (Bi_(1-x)In_x)_2Se_3 thin films

摘要

We use time-resolved THz spectroscopy to study microscopic conductivity and photoinduced carrier dynamics in MBE-grown 100 nm thick (Bi_(1-x)In_x)_2Se_3 thin films with indium concentration varying from x=0 to x=0.5. Both intrinsic and photoinduced conductivity in Bi2Se3 is significantly higher compared to the films with x=0.25 and x=0.50, with carriers that are not constrained by the twin domain boundaries and exhibit high mobility of 1100 cmVVs. We find that introducing indium with concentration of x=0.25 and higher, above the threshold for a topological to trivial transition, suppresses both intrinsic and photoinduced conductivity by over an order of magnitude and reduces the lifetime of photoexcited carriers. These findings demonstrate that controlling indium concentration in (Bi_(1-x)In_x)_2Se_3 films provides an avenue to design (Bi_(1-x)In_x)_2Se_3 films with desired properties for high-speed optoelectronic devices.