Light-induced negative differential resistance in graphene/Si-quantum-dot tunneling diodes.

Kyeong Won Lee,Euyheon Hwang,Chan Wook Jang,Sung Kim,Soo Seok Kang,Dong Hee Shin,Jong Min Kim,Dae Hun Lee,Suk-Ho Choi

doi:10.1038/srep30669

Abstract

One of the interesing tunneling phenomena is negative differential resistance (NDR), the basic principle of resonant-tunneling diodes. NDR has been utilized in various semiconductor devices such as frequency multipliers, oscillators, relfection amplifiers, logic switches, and memories. The NDR in graphene has been also reported theoretically as well as experimentally, but should be further studied to fully understand its mechanism, useful for practical device applications. Especially, there has been no observation about light-induced NDR (LNDR) in graphene-related structures despite very few reports on the LNDR in GaAs-based heterostructures. Here, we report first observation of LNDR in graphene/Si quantum dots-embedded SiO2 (SQDs:SiO2) multilayers (MLs) tunneling diodes. The LNDR strongly depends on temperature (T) as well as on SQD size, and the T dependence is consistent with photocurrent (PC)-decay behaviors. With increasing light power, the PC-voltage curves are more structured with peak-to-valley ratios over 2 at room temperature. The physical mechanism of the LNDR, governed by resonant tunneling of charge carriers through the minibands formed across the graphene/SQDs:SiO2 MLs and by their nonresonant phonon-assisted tunneling, is discussed based on theoretical considerations.

Highlights

Schematics of (a,b) graphene/Si quantum dots (SQDs):SiO2 MLs heterostructures for typical large and small SQD sizes, respectively. (c–e) Band diagrams under forward and reverse biases, respectively, while illuminated
We report novel features of light-induced NDR (LNDR) first found in graphene/SQDs:SiO2 MLs heterojunction tunneling diodes
The LNDR behaviors strongly depend on SQD size (d), temperature (T), and irradiance power (P), and are well explained by resonant tunneling of charge carriers through the miniband formed across the graphene/SQDs:SiO2 MLs and by their nonresonant phonon-assisted tunneling

Summary

Introduction

Schematics of (a,b) graphene/SQDs:SiO2 MLs heterostructures for typical large and small SQD sizes, respectively. (c–e) Band diagrams under forward (miniband conduction) and reverse (miniband and phononassisted conductions) biases, respectively, while illuminated. Schematics of (a,b) graphene/SQDs:SiO2 MLs heterostructures for typical large and small SQD sizes, respectively. P-n tunneling diodes[15], field effect transistors[34,35], prompted by the unique two-dimensional properties of graphene at the nanoscale. We report novel features of light-induced NDR (LNDR) first found in graphene/SQDs:SiO2 MLs heterojunction tunneling diodes. The LNDR behaviors strongly depend on SQD size (d), temperature (T), and irradiance power (P), and are well explained by resonant tunneling of charge carriers through the miniband formed across the graphene/SQDs:SiO2 MLs and by their nonresonant phonon-assisted tunneling. The T dependence of the LNDR properties is consistent with that of the lifetimes found in photocurrent (PC)-decay curves. As P increases, the photo I-V curves are more structured with the peak-to-valley ratios from ∼1.5 to ∼2.2 at room temperature, possibly originating from electric-field screening due to space charge buildup and state filling

Methods

Results

Conclusion