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Nanoscale Photodetector Could Advance, Miniaturize Optoelectronics

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MADISON, Wis. and BUFFALO, N.Y., July 10, 2017 — Using a high-yield, high-throughput fabrication method, nanometer-thin photodetectors with enhanced light absorption have been demonstrated. The photodetectors, which are based on a nanocavity interference mechanism, could enable miniaturization of optoelectronic devices, leading to performance gain without adding bulk.

The research addressed two remaining challenges to the thinning of photoactive layers to the nanometer scale: how to prevent incomplete photon absorption and low quantum efficiency due to weak light-matter interaction and how to maintain single-crystalline quality in the ultrathin material.

The device was developed by researchers at the University of Wisconsin-Madison (UW-Madison) and the University at Buffalo (UB). It consists of nanocavities sandwiched between a top layer of ultrathin single-crystal germanium and a reflecting layer of silver. The nanocavity structures used for the device have been shown, in previous work by the researchers, to increase the amount of light that thin semiconducting materials, e.g. germanium, can absorb.

Nanoscale photodetector, University of Wisconsin-Madison and University at Buffalo.
Shrinking photodetectors like this one, created and tested in the laboratory of UW-Madison engineering Professor Zhenqiang (Jack) Ma, help make consumer electronics smaller. Courtesy of Stephanie Precourt/UW-Madison.

“Because of the nanocavities, the photons are ‘recycled’ so light absorption is substantially increased — even in very thin layers of material,” said UW-Madison professor Zhenqiang (Jack) Ma.

To manage the quality of the germanium thin films, researchers used a novel membrane-transfer technology that allowed them to integrate single crystalline semiconducting materials onto a substrate. This resulted in a very thin, yet effective, light-absorbing photo detector for smaller optoelectronics applications.

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“It is an enabling technology that allows you to look at a wide variety of optoelectronics that can go to even smaller footprints, smaller sizes,” said professor Zongfu Yu of UW-Madison, who conducted computational analysis of the detectors.

While the advance was demonstrated using a germanium semiconductor, the researchers believe that their method could be applied to other semiconductors.

“And importantly, by tuning the nanocavity, we can control what wavelength we actually absorb,” said professor Qiaoqiang Gan from UB. “This will open the way to develop lots of different optoelectronic devices.”

Nanoscale photodetector, University of Wisconsin-Madison and University at Buffalo.
UW-Madison electrical and computer engineering graduate student Zhenyang Xia holds a dish containing photodetector samples. The sample colors vary depending on how they are tuned to absorb a specific light wavelength. Courtesy of Stephanie Precourt/UW-Madison.

Smaller optoelectronic devices could be used to reduce the size and weight of solar panels and to speed data transmission.

The researchers are applying jointly for a patent on the technology through the Wisconsin Alumni Research Foundation.

The research was published in Science Advances (doi: 10.1126/sciadv.1602783).

Published: July 2017
Glossary
nanopositioning
Nanopositioning refers to the precise and controlled movement or manipulation of objects or components at the nanometer scale. This technology enables the positioning of objects with extremely high accuracy and resolution, typically in the range of nanometers or even sub-nanometer levels. Nanopositioning systems are employed in various scientific, industrial, and research applications where ultra-precise positioning is required. Key features and aspects of nanopositioning include: Small...
optoelectronics
Optoelectronics is a branch of electronics that focuses on the study and application of devices and systems that use light and its interactions with different materials. The term "optoelectronics" is a combination of "optics" and "electronics," reflecting the interdisciplinary nature of this field. Optoelectronic devices convert electrical signals into optical signals or vice versa, making them crucial in various technologies. Some key components and applications of optoelectronics include: ...
nano
An SI prefix meaning one billionth (10-9). Nano can also be used to indicate the study of atoms, molecules and other structures and particles on the nanometer scale. Nano-optics (also referred to as nanophotonics), for example, is the study of how light and light-matter interactions behave on the nanometer scale. See nanophotonics.
photodetector
A photodetector, also known as a photosensor or photodiode, is a device that detects and converts light into an electrical signal. Photodetectors are widely used in various applications, ranging from simple light sensing to more complex tasks such as imaging and communication. Key features and principles of photodetectors include: Light sensing: The primary function of a photodetector is to sense or detect light. When photons (particles of light) strike the active area of the photodetector,...
Research & TechnologyeducationAmericasMaterialsmaterials processingNanopositioningoptoelectronicsSensors & Detectorsnanosolarphotodetectorthin-film materials

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