Publication

Enhanced Optoelectronic Performance of a Passivated Nanowire-based Device: Key Information from Real-space Imaging using 4D Electron Microscopy

Enhanced Optoelectronic Performance of a Passivated Nanowire-based Device: Key Information from Real-space Imaging using 4D Electron Microscopy
Jafar I. Khan, Aniruddha Adhikari, Jingya Sun, Davide Priante, Riya Bose, Basamat S. Shaheen, Tien Khee Ng, Chao Zhao, Osman M. Bakr, Boon S. Ooi, Omar F. Mohammed
Small, 12(17), pp 2313-2320, (2016)​

Jafar I. Khan, Aniruddha Adhikari, Jingya Sun, Davide Priante, Riya Bose, Basamat S. Shaheen, Tien Khee Ng, Chao Zhao, Osman M. Bakr, Boon S. Ooi, Omar F. Mohammed
4D Ultrafast microscopy, charge carrier dynamics, passivation, InGaN nanowires, carrier recombination
2016

 


Semiconductor nanowires (NWs) are a promising class of active materials for optoelectronic devices. However, in these semiconductor NW-based optoelectronics, managing surface trap states and understanding their role on the ultrafast charge- carrier dynamics, particularly, at the surface and interfaces remains as a major bottleneck preventing further advancements and commercial exploitation of these nanoscale material devices. A key challenge is to selectively map such ultrafast dynamical processes on the surfaces of NWs, a capability so far out of reach of purely optical probing time-resolved laser techniques. Selective mapping of surface dynamics in real space and time can only be achieved by applying four-dimensional scanning ultrafast electron microscopy (4D S-UEM). In this work, we spatially and temporally visualize the charge carrier dynamics on the surface of InGaN NW arrays before and after surface passivation with octadecylthiol (ODT) using 4D S-UEM with nanometer spatial and sub-picosecond temporal resolutions. The time-resolved secondary electron (SE) images clearly demonstrate that carrier recombination on the NW surface is significantly slowed down after ODT treatment, providing clear evidence of the minimization of the surface defects. This observation is fully supported by elemental mapping of the NWs which shows removal of surface oxygen along with formation of carbon rich amorphous layer on the surface after ODT treatment and enhancement of the performance of the light emitting device. Direct observation of surface dynamics provides a profound understanding of the photo-physical mechanisms on materials’ surfaces and enables the formulation of effective surface trap states management strategies for the next generation of high performance NW based optoelectronic devices.

 

DOI: 10.1002/smll.201503651