Characterizations of Topological Sb2Te3/Bi2Te3 Heterostructures and the application for photodetector

Abstract

In this research We grow Sb2Te3/Bi2Te3 heterostructure on sapphire (0001) substrate by the MBE system At the interface diffusion of Sb and Bi causes the ternary compounds and tuning fermi level By adjusting the thickness we can tuning Fermi level to the dirac point and form an ideal topological insulator We confirmed this result through ARPES and hall measurements In Hall measurement carrier type transition occurs between 7/10nm and 8/10nm The change of carrier type also appeared in ARPES measurement At this time Surface state replaces bulk state as the main contributor to carrier transport On the other hand Sb2Te3/Bi2Te3 heterostructure has a p-n junction at the interface The built-in potential at the interface can effectively separate the electron-hole pairs in TI and suppress the rapid recombination of carriers leading to an outstanding photo responsivity At the same time as the carrier type changes the largest depletion region will occur at the interface This can effectively separate the electron-hole pairs and lead to the maximum photo responsivity Finally we obtain maximum responsivity of the photodetector measured under 632 8 nm light illumination at 7/10 nm Sb2Te3/Bi2Te3 The photodetector possessed a large light responsivity of 167 A/W The result of photodetector measurement correlates with the conclusion of Hall measurement

Date of Award	2019
Original language	English
Supervisor	Sheng-Hao Tseng (Supervisor)