Observations of two-dimensional quantum oscillations and ambipolar transport in the topological insulator Bi2Se3 achieved by Cd doping

TL;DR

This study demonstrates defect engineering in Bi2Se3 to achieve high resistivity and observe quantum oscillations, revealing ambipolar transport and two-dimensional quantum effects through controlled doping and annealing.

Contribution

It introduces a novel defect-engineering approach combining Cd doping and annealing to optimize transport and observe quantum oscillations in Bi2Se3.

Findings

High bulk resistivity exceeding 0.5 Ohmcm at 1.8 K

Observation of two-dimensional Shubnikov-de Haas oscillations

Demonstration of ambipolar transport in Bi2Se3

Abstract

We present a defect-engineering strategy to optimize the transport properties of the topological insulator Bi2Se3 to show a high bulk resistivity and clear quantum oscillations. Starting with a p-type Bi2Se3 obtained by combining Cd doping and a Se-rich crystal-growth condition, we were able to observe a p-to-n-type conversion upon gradually increasing the Se vacancies by post annealing. With the optimal annealing condition where a high level of compensation is achieved, the resistivity exceeds 0.5 Ohmcm at 1.8 K and we observed two-dimensional Shubnikov-de Haas oscillations composed of multiple frequencies in magnetic fields below 14 T.