Exciton Drift in Semiconductors under Uniform Strain Gradients: Application to Bent ZnO Microwires

Significance Statement:

Scientists from Nanostructure and low dimensional physics laboratory of Peking University and Quantum Optoelectronics Laboratory of École polytechnique fédérale de Lausanne demonstrated the exciton drift driven by uniform elastic strain gradient in ZnO microwires. The pure bending deformation in ZnO microwires results in spatial variation of exciton energy, and the exciton energy gradient will induce the exciton drift, which was directly observed by the unique picosecond cathodoluminescence. They demonstrated that the strain gradient can be effectively used to tune the exciton and carrier dynamics in semiconductors.

Journal Reference

ACS Nano, 2014, 8 (4), pp 3412–3420.

Xuewen Fu †, Gwenole Jacopin ‡, Mehran Shahmohammadi ‡, Ren Liu †, Malik Benameur §,Jean-Daniel Ganière ‡, Ji Feng ⊥, Wanlin Guo ∥,Zhi-Min Liao †, Benoit Deveaud ‡*, Dapeng Yu†*

^† State Key Laboratory for Mesoscopic Physics, and Electron Microscopy Laboratory, Department of Physics,Peking University, 209 Chengfu Road, Beijing 100871, China and

^‡ Laboratoire d’Optoélectronique Quantique, École Polytechnique Fédérale de Lausanne (EPFL), Station 3, CH-1015 Lausanne, Switzerland and

^§ Attolight AG, EPFL Innovation Square, PSE D, 1015 Lausanne, Switzerland and

^⊥ International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China and

^∥ State Key Laboratory of Mechanics and Control of Mechanical Structures and Institute of Nano Science,Nanjing University of Aeronautics and Astronautics, 29 Yudao Street, Nanjing 210016, China.

Abstract

Optimizing the electronic structures and carrier dynamics in semiconductors at atomic scale is an essential issue for innovative device applications. Besides the traditional chemical doping and the use of homo/heterostructures, elastic strain has been proposed as a promising possibility. Here, we report on the direct observation of the dynamics of exciton transport in a ZnO microwire under pure elastic bending deformation, by using cathodoluminescence with high temporal, spatial, and energy resolutions. We demonstrate that excitons can be effectively drifted by the strain gradient in inhomogeneous strain fields. Our observations are well reproduced by a drift-diffusion model taking into account the strain gradient and allow us to deduce an exciton mobility of 1400 ± 100 cm²/(eV s) in the ZnO wire. These results propose a way to tune the exciton dynamics in semiconductors and imply the possible role of strain gradient in optoelectronic and sensing nano/microdevices.

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Exciton Drift in Semiconductors under Uniform Strain Gradients: Application to Bent ZnO Microwires

Abstract

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