Capacitance-voltage measurements of (Bi$_{1-x}$Sb$_x$)$_2$Te$_3$ field effect device

TL;DR

This study investigates the capacitance-voltage characteristics of (Bi$_{1-x}$Sb$_x$)$_2$Te$_3$ topological insulator devices, revealing frequency, temperature, and illumination effects, as well as hysteresis due to surface states.

Contribution

It provides detailed C-V measurements of topological insulator devices, highlighting the influence of surface states and measurement conditions on device behavior.

Findings

Frequency and temperature dependence of C-V traces

Presence of hysteresis linked to surface states

Impact of illumination on device capacitance

Abstract

Capacitance-voltage ($\textit{C-V}$) traces in n-type-(Bi$_{1-x}$Sb$_x$)$_2$Te$_3$/oxide/metal capacitor structures using an AC capacitance bridge are investigated. By tuning the top gate voltage from positive to negative values, the system at the interface is tuned from accumulation, via depletion into inversion. Our results show the typical low-frequency and high frequency $\textit{C-V}$ traces, depending on measuring frequency, temperature and illumination intensity and reflecting their sensitive dependence on recombination/generation rates. Superimposed a strong hysteresis under inversion is also observed which is ascribed to the presence of conventional localized surface states which coexist with topological surface states.