A 30 μm Coaxial Nanowire Photoconductor Enabling Orthogonal Carrier Collection

Area of Science:

• Nanotechnology
• Materials Science
• Optoelectronics

Background:

• Photodetectors are crucial for optical sensing.
• Improving photodetector performance, such as gain and response time, is an ongoing challenge.
• Core-multishell nanowire architectures offer unique properties for device applications.

Purpose of the Study:

• To design and fabricate a monolithic, coaxial, three-layer Au-CdSe-Au nanowire photodetector.
• To investigate the influence of the CdSe shell thickness on photodetector performance.
• To optimize the device architecture for enhanced photoconductive gain and accelerated response/recovery.

Main Methods:

• Fabrication of Au-CdSe-Au nanowires using lithographically patterned nanowire electrodeposition (LPNE) and electrodeposition.
• Characterization of nanostructure, layer thickness, and composition using SEM, FIB, and EDS.
• Probing position-dependent photoresponse along the nanowire axis using a laser spot.

Main Results:

• Successfully fabricated a 30 μm long Au-CdSe-Au nanowire photodetector with a core-multishell structure.
• Demonstrated that the Au nanoshell significantly enhances photocurrent.
• Identified optimal CdSe shell thickness (dCdSe = 250 nm) yielding a photoconductive gain of 2172, responsivity of 209 A·W⁻¹, response time of 17 μs, and recovery time of 96 μs.

Conclusions:

• The Au-CdSe-Au core-multishell nanowire architecture enables high-performance monolithic photodetectors.
• Device performance is highly sensitive to CdSe shell thickness, with an optimal range identified.
• This design maximizes photoconductive gain and photoresponsive area while achieving fast response and recovery times.