July 7, 2017 by Renee Meiller Shrinking photodetectors like this one, created and tested in the laboratory of UW-Madison engineering Professor Zhenqiang (Jack) Ma, help make consumer electronics smaller. Credit: Stephanie Precourt\/UW-Madison <\/p>\n
In today's increasingly powerful electronics, tiny materials are a must as manufacturers seek to increase performance without adding bulk. <\/p>\n
Smaller also is better for optoelectronic deviceslike camera sensors or solar cellswhich collect light and convert it to electrical energy. Think, for example, about reducing the size and weight of a series of solar panels, producing a higher-quality photo in low lighting conditions, or even transmitting data more quickly. <\/p>\n
However, two major challenges have stood in the way: First, shrinking the size of conventionally used \"amorphous\" thin-film materials also reduces their quality. And second, when ultrathin materials become too thin, they become almost transparent and actually lose some ability to gather or absorb light. <\/p>\n
Now, in a nanoscale photodetector that combines a unique fabrication method and light-trapping structures, a team of engineers from the University of Wisconsin-Madison and the University at Buffalo has overcome both of those obstacles. <\/p>\n
The researcherselectrical engineering professors Zhenqiang (Jack) Ma and Zongfu Yu at UW-Madison and Qiaoqiang Gan at Buffalodescribed their device, a single-crystalline germanium nano-membrane photodetector on a nano-cavity substrate, today (July 7, 2017) in the journal Science Advances. <\/p>\n
\"The idea, basically, is you want to use a very thin material to realize the same function of devices in which you need to use a very thick material,\" says Ma. <\/p>\n
The device consists of nano-cavities sandwiched between a top layer of ultrathin single-crystal germanium and a reflecting layer of silver. <\/p>\n
\"Because of the nano-cavities, the photons are 'recycled' so light absorption is substantially increasedeven in very thin layers of material,\" says Ma. <\/p>\n
Nano-cavities are made up of an orderly series of tiny, interconnected molecules that essentially reflect, or circulate, light. Gan already has shown that his nano-cavity structures increase the amount of light that thin semiconducting materials like germanium can absorb. <\/p>\n
However, most germanium thin films begin as germanium in its amorphous formmeaning the material's atomic arrangement lacks the regular, repeating order of a crystal. That also means its quality isn't sufficient for increasingly smaller optoelectronics applications. <\/p>\n
That's where Ma's expertise comes into play. A world expert in semiconductor nano-membrane devices, Ma used a revolutionary membrane-transfer technology that allows him to easily integrate single crystalline semiconducting materials onto a substrate. <\/p>\n
The result is a very thin, yet very effective, light-absorbing photodetectora building block for the future of optoelectronics. <\/p>\n
\"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,\" says Yu, who conducted computational analysis of the detectors. <\/p>\n
While the researchers demonstrated their advance using a germanium semiconductor, they also can apply their method to other semiconductors. <\/p>\n
\"And importantly, by tuning the nano-cavity, we can control what wavelength we actually absorb,\" says Gan. \"This will open the way to develop lots of different optoelectronic devices.\" <\/p>\n
Explore further: This 'nanocavity' may improve ultrathin solar panels, video cameras and more <\/p>\n
More information: \"Single-crystalline germanium nanomembrane photodetectors on foreign nanocavities\" Science Advances (2017). advances.sciencemag.org\/content\/3\/7\/e1602783<\/p>\n
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Powerful new photodetector can enable optoelectronics advances - Phys.Org<\/a><\/p>\n","protected":false},"excerpt":{"rendered":" July 7, 2017 by Renee Meiller Shrinking photodetectors like this one, created and tested in the laboratory of UW-Madison engineering Professor Zhenqiang (Jack) Ma, help make consumer electronics smaller. Continue reading