Prof. Hong-Gyu Park’s team develops photon-triggered nanowire transistors
New applications include high-resolution cameras and photonic computers

 
▲ Prof. Hong-Gyu Park (left, corresponding author) and post-doc researcher Jungkil Kim (right, first author) 

A team led by Prof. Hong-Gyu Park of the Department of Physics under the College of Sciences developed nanowire transistors that control electronic signals using photons and efficiently amplify currents. 
* Nanowire: A nanostructure with a diameter of the order of a nanometer and a length measuring tens of micrometers. It is used in lasers, transistors, memories, and chemical-detecting sensors.
* Transistor: A semiconductor device connected to an external circuit to amplify or switch electronic signals.

The team’s research was published in Nature Nanotechnology on August 8. The study received funding from the Basic Research Support Program of the Ministry of Science and ICT.
 - Title of the Article: Photon-triggered nanowire transistors
 - Author Information: Prof. Hong-Gyu Park (corresponding author, Korea University), post-doc researcher Jungkil Kim (first author, Korea University)

Transistors, a key component of modern electronic devices, are used to amplify or switch electronic signals. While past studies have attempted to improve their efficiency by using nanosized transistors or exposing them to light, commercialization has not been achieved due to the complex processes and poor yield.

By partially inserting porous silicon into silicon nanowires, the team developed nanowire transistors capable of using photons to effectively control electronic signals. The new transistors have significantly lowered the complexity of existing semiconductor design and manufacturing processes.

* Porous silicon: Silicon containing nanopores (one nanometer is one billionth of a meter) in its microstructure.

Porous silicon has a very low current because of nanopores in its microstructure. The team made use of this poor conductivity, and discovered for the first time that current is significantly amplified when porous silicon is exposed to light. In addition, a new logic gate was created by fabricating transistors with two porous silicon segments in a single silicon nanowire. A high submicrometer-resolution photodetector system was established using thin nanowire transistors containing several porous silicon segments.
 
* Logic gate: A basic block of a digital circuit with two output states for a given input of 1 or 0. Used in computational devices of computers and controllers.
* Photodetector: A device that detects light photons and converts them into current.

Prof. Hong-Gyu Park said, “Our study shows that nanowires alone can be used to fabricate all kinds of electronic devices by focusing lasers on porous silicon after placing them in desired positions. We expect these transistors to have various applications, including ultrasensitive high-resolution cameras and photonic computers.” 
 

[ Terminology ]

1. Nature Nanotechnology
 ○ Nature Nanotechnology, a journal by the renowned Nature Publishing Group, has been published since 2006. With an impact factor of 38.986, it was ranked as the top journal in the field of nanosciences and nanotechnology by Thomson JCR.
 
2. Transistor
 ○ A semiconductor device connected to an external circuit to amplify or switch electronic signals.

3. Porous silicon
 ○ Silicon containing nanopores (one nanometer is one billionth of a meter) in its microstructure.

4. Nanowire
 ○ A nanostructure with a diameter of the order of a nanometer, and a length measuring tens of micrometers. It is used in lasers, transistors, memories, and chemical-detecting sensors. 

5. Logic gate
 ○ A basic block of a digital circuit with two output states for a given input of 1 or 0. Used in computational devices of computers and controllers.

6. Photodetector
 ○ A device that detects light photons and converts them into current.

[ Figure Description ]

Figure 1. Photon-triggered silicon nanowire transistors
Schematic illustration showing changes in electrical properties as a result of focusing lasers on the porous silicon segment of nanowires.

Figure 2. Photon-triggered silicon nanowire transistors
SEM images of porous silicon (PSi) partially inserted into crystal silicon (CSi) nanowires (left). Current increases with light intensity when lasers are focused on the porous silicon (right). Current increased by up to ten million times. 

Figure 3. Photon-triggered silicon NAND logic gate
A NAND logic gate with two lasers focused on each porous silicon segment (left). The input value is 1 when the lasers are turned on, and 0 when turned off. For input values of 00, 01, and 10, the output value is 1 (5V). When the input value is 11, the output becomes 0 (3.75 V) (right).