Electrostatics and quantum efficiency simulations of asymmetrically contacted carbon nanotube photodetector

Xiao Guo,Sheng Wang,Lian-Mao Peng

doi:10.1063/1.5000759

Abstract

Electrostatic properties of asymmetrically contacted carbon nanotube barrier-free bipolar diode photodetector are studied by solving the Poisson equation self-consistently with equilibrium carrier statistics. For electric field parallel to tube’s axis, the maximum electric field occurs near contact but decays rapidly in a few nanometers, followed by a slowly increasing trend when it extends to the center of channel. By considering the field ionization and the diffusion effect of exciton, a model of estimation on quantum efficiency for the device is made. We find that the quantum efficiency increases with increasing exciton lifetime, decreasing diffusion constant and channel length. For devices with a channel length shorter than 50 nm, the contribution of field ionization to the quantum efficiency can reach 60%.

Highlights

Semiconducting single-walled carbon nanotubes (SWCNTs) are considered to be a promising optoelectronic material because of their high absorption coefficient,[1] high mobility,[2] and tunable spectral response with their diameter and chirality.[3]
The optical absorption of SWCNTs is dominated by excitons with binding energies of hundreds of meV4–7 and exciton dissociation becomes a critical issue for SWCNT based photodetector
In early reports,[8,9] electric field has been considered to be an important factor in exciton dissociation in carbon nanotubes (CNTs), so the electric field profiles play a key role in the performance of CNT based photodetectors

Summary

Introduction

Semiconducting single-walled carbon nanotubes (SWCNTs) are considered to be a promising optoelectronic material because of their high absorption coefficient,[1] high mobility,[2] and tunable spectral response with their diameter and chirality.[3]. Electrostatics and quantum efficiency simulations of asymmetrically contacted carbon nanotube photodetector With regard to the p-n junction diodes, several works have revealed the electrostatic properties and quantum efficiency of the devices.[11,12,13,14] But the conclusions might not be suitable for BFBDs because of the different structures.

Results

Conclusion