KAIST EE Prof. Shinhyun Choi’s team develop highly reliable synthetic synapse transistor

[Seok-Ho Seo (M.S. candidate), Dong-Hoon Kim (M.S.), Beom-Jin Kim (M.S.), Seung-Woo Park (M.S. candidate), Professor Shinhyun Choi]


KAIST EE professor Shinhyun Choi and his research team announced on 16th that they successfully developed a synthetic synapse transistor, whose durability allows it to perform repetitive operations with high reliability. The developed transistor, which emulates the behaviors of a neurotransmitter in a human brain, can also increase the learning accuracy of artificial intelligence (AI) without requiring additional circuits. By not only exploiting the structure utilized in conventional NAND Flash memory but also successfully coping with its low durability, Professor Choi and his research team were able to develop the transistor that can reliably play the role of a synapse. 


This research accomplishment was published in the October editorial of Nature communications under the title of “The gate injection-based field-effect synapse transistor with linear conductance update for online training”, in which Seok-Ho Seo (M.S. candidate), Dong-Hoon Kim (M.S.), Beom-Jin Kim (M.S.), and Seung-Woo Park (M.S. candidate) were all listed as co-first authors. 


KAIST EE M.S. candidate Seok-Ho Seo stated that “In addition to this research project, I want to keep on developing novel device technologies for neuromorphic computing.”

This research was supported in part by National Research Foundation of Korea, Korea Evaluation Institute of Industrial Technology, National NanoFab center, and Samsung Science & Technology Foundation.


EE Prof. Hyunjoo Jenny Lee’s team : sleep deprivation and short-term memoery therapy with brainwave monitoring and ultrasound stimulation

[KAIST EE Prof. Hyunjoo Jenny Lee , Ph.D. candidate Yehhyun Jo, KBRI  Dr. Jeongyeon Kim, from left]

 On Nov. 8th, Professor Hyunjoo Jenny Lee (KAIST EE) and Dr. Jeongyeon Kim (Korea Brain Research Institute, KBRI) announced a joint development of a general-purpose ultrasound stimulation and monitoring system for the brain activity of small animals.


This technology can stimulate the brain depending on the sleeping condition monitored in real-time, and the research team demonstrated that sleep patterns and short-term memory could be controlled through stimulation of the prefrontal cortex (PFC) during the non-rapid-eye movement (NREM) sleep cycle.

 The conventional ultrasound stimulation systems are either too large to be used on free-moving mice, or difficult to use for simultaneous measurements due to large noise signals.


Professor Hyunjoo Lee’s team sought to solve these issues through MEMS-based CMUT (Capacity Micromachined Ultrasound Transducer) research and was able to develop a customizable, closed-loop system that stimulates the brain based on its current state. Their closed-loop stimulation algorithm is able to analyze the sleep phase every 6 seconds and deliver ultrasound stimulation during the NREM sleep cycle, both in a simultaneous process without significant noise. Stimulating the PFC of sleep-deprived mice for 10 hours during NREM sleep cycle showed an increase in rapid-eye movement (REM) sleep duration and short-term spatial memory protection from acute sleep deprivation.


“Ultrasound is a very safe human body irradiation technology, enough that it is used even for fetal imaging”, says Professor Hyunjoo Jenny Lee, “and it is a very attractive means of noninvasive treatment because its radiation can be intensively focused deep inside the body without spreading.” She added, “however, there is little research on the efficacy of ultrasound stimulation due to the lack of preclinical stimulation systems. I hope that our work could be used by many brain science research teams in discovering various therapeutic effects of ultrasound.”


The study was led by Ph.D. candidate Yehhyun Jo (KAIST EE) under professor Hyunjoo Lee, and Dr. Jeongyeon Kim’s research team, with participation of Seong-Gi Kim (Head of Center for Neuroscience Imaging Research, Institute of Basic Science), Dr. Byung Chul Lee (KAIST), and professor Greg S.B. Suh (KAIST Department of Biological Sciences). Their work was published on Oct. 19th in the international journal Advanced Science, and was selected as the Research Headline by the publisher Wiley. (Title: General-purpose ultrasound neuromodulation system for chronic, closed-loop preclinical studies in freely behaving rodents)


This research was supported by the Next Generation Intelligence Semiconductor Program through National Research Foundation (NRF) funded by the Ministry of Science and ICT (MSIT), the Engineering Research Center of Excellence (ERC) Program, Korea Brain Research Institute’s Basic Research Program, and the Korea Medical Device Development Fund.


Reference link : 


EE Prof. Shinhyun Choi’s team, selected for Nature Communications Editors’ highlight

[Ph.D. candidate See-On Park, Ph.D. candidate Hakcheon Jeong, Master course Jong-Yong Park and Professor Shinhyun Choi, From left] 


See-On Park, Hakcheon Jeong, Jong-Yong Park, researchers under EE Professor Shinhyun Choi, developed a highly reliable variable resistor (memristor) array that simulates the behavior of neurons using a metal oxide layer with an oxygen concentration gradient, and published their work in Nature Communications.

The study was selected for the Nature Communications’ Editor’s highlight, as well as for the Featured Image on the journal website’s front page. 


Link : https://www.nature.com/ncomms/


At KAIST, their research was introduced as one of the breakthrough researches of Fall 2022 within the College of Engineering. 


[Figure 1. The Featured Image in the Nature Communications front page introducing the KAIST team’s research on the memristor for artificial neurons] 


(Thesis title: Experimental demonstration of highly reliable dynamic memristor for artificial neuron and neuromorphic computing) 

This research was conducted with the support from the Samsung Research Funding & Incubation Center of Samsung Electronics



EE Prof. Sanghun Jeon receives commendation from The Ministry of Trade, Industry, and Energy at the 15th Semiconductor Day

[Professor Sanghun Jeon]


KAIST EE Professor Sanghun Jeon received commendation from the Ministry of Trade, Industry, and Energy at the 15th Semiconductor Day. 


Celebrating its 15th anniversary this year, Semiconductor day is an annual event in which those who contributed to the development of the semiconductor industry are recognized and commended for their efforts in the field of industry, academia, and research.


It first started in order to celebrate October of 1994, the first year in which the export of semiconductor for South Korea reached over 10 billion US dollars for the first time ever. The event holds special significance this year in that 2022 marks the 32th anniversary of Korea Semiconductor Industry Association (KSIA, founded in November 11th, 1991), infusing the semiconductor industry with hope of overcoming new challenges through innovation.


Sanghun Jeon was nominated for the commendation from the Ministry of Trade, Industry, and Energy thanks to his worldwide leadership and contribution in innovating thin-film processes and device manufacturing, creating research breakthroughs that help the commercialization of ferroelectric hafnium devices that are highly suitable for CMOS process.


Unlike the conventional devices whose computational capabilities are constrained by Moore’s law and von Neumann computer architectures and thereby impose significant limitation on device performance and energy efficiency, ferroelectric hafnium devices are expected to bring into reality Edge Intelligence (EI), which allows the local analysis of dataset and autonomous decision-making.


Sanghun Jeon and his research lab are developing key effective technologies related to ferroelectric hafnium devices, which are expected to play a key role in future device industry. The relevant research accomplishments were presented at IDEM 2021, one of the most prestigious conferences in the field of electronic devices.

They will also be presented at IDEM 2022. 


EE Prof. Kayoung Lee, a prestigious award for under 40 year researcher from Korean Graphene Society

[Prof. Kayoung Lee]


KAIST EE Professor Kayoung Lee is selected for the Young Scholar Award at the 9th Korean Symposium on Graphene and 2D Materials, hold by the Korean Graphene Society. 


The Young Scholar Award is awarded to those who have made a great contribution to the Korean graphene and 2D materials field, among academics under the age of 40. 


Professor Kayoung Lee, as this year’s awardee, received the award with a prize of 1 million wons.


[Award ceremony picture, Society Chair, Prof. Jong-Hyun Anh, Prof. Kayoung Lee, from left ]

EE PhD candidate, Dong-gyun Lee (Prof. Seung-hyeop Yoo’s Lab) is awarded the 2022 APC Student Paper Prize

[ EE P.H.D candidate Dong-gyun Lee, Prof. Seung-hyeop Yoo, from left]
At the 2022 Advanced Photonics Congress held in July of this year, PhD candidate Dong-gyun Lee of Electrical Engineering department was awarded the Congress Student Paper Prize.
This conference is a global conference where leading researchers from around the world gather and share research on optical materials, optical signal processing, optical communications, and integrated optics. 
Based on rigorous mechano-optical analysis and using ultra-thin PI and elastomer arrays, Lee proposed a new method to increase the area ratio, which has been a bottleneck in stretchable organic light-emitting diode platforms.
For this contribution, he won the 2022 Advanced Photonics Congress Student Paper Prize by The Optical Devices and Materials for Solar Energy and Solid-state Lighting (PVLED) committee chair.

Ph.D. candidate Simok Lee (Prof. Jae-Woong Jeong) wins Best Presentation Paper Award

[Prof. Jae-Woong Jeong, Simok Lee, From Left ]


Ph.D. student Simok Lee (Advised by Jae-Woong Jeong) won the Best Paper Award at the 2022 Korean Sensors Society Autumn Conference.

The Korean Sensors Society Conference is a conference held every spring and fall, and this year, and this autumn conference was held in Yeosu from August 24th to 26th.

Ph.D. student Simok Lee has published a paper titled “Adaptive Electronic Skin with High Sensitivity and Large Bandwidth Based on Gallium Microdrop-Elastomer Composite”.

Details are follows. Congratulations once again to Ph.D. student Simok Lee and Professor Jae-Woong Jeong!


Conference: 2022 Korean Sensors Society Autumn Conference


Date: August 24-26, 2022


Award: Best Presentation Paper Award


Authors: Simok Lee, Sang-Hyuk Byun, Jae-Woong Jeong (Advisory Professor)


Paper Title: Adaptive Electronic Skin with High Sensitivity and Large Bandwidth based on Gallium Microdroplet-Elastomer Composite



Prof. Jun-Bo Yoon’s team selected as ACS Nano 2022 Supplementary cover paper for develpment of highly reliable wireless Hydrogen gas sensor

TITLE: EE Professor Jun-Bo Yoon’s research team developed a highly sensitive and reliable wireless Hydrogen gas sensor through phase-transition-inhibited Pd nanowires, and is selected as a supplementary cover paper.
A research team consisting of KAIST’s School of Electrical Engineering Professor Jun-Bo Yoon and Busan National University’s Professor Min-Ho Seo (KAIST Ph.D graduate) has developed a method for wireless and linear Hydrogen detection with high sensitivity, and the paper was accepted to ACS Nano 2022 (Min-Seung Jo as the first author). The research team successfully built a sensor that exhibits high sensing linearity and stable sensitivity over Hydrogen gas concentrations of 0~4% using 3-dimensional Pd nanowire structures that exhibit Pd phase-transition-inhibitions. 
*Phase-transition: physical processes of transition between a state of a medium (such as solid, liquid, and gas phase) used in chemistry and thermodynamics
The research, led by a Ph.D candidate student Min-Seung Jo as the first author, has been published in a well-known international journal ACS Nano on May 2022. (Paper: Wireless and Linear Hydrogen Detection up to 4% with High Sensitivity through Phase-Transition-Inhibited Pd Nanowires) (https://pubs.acs.org/doi/10.1021/acsnano.2c01783).
Hydrogen gas has gaining attention as the next generation environmentally friendly energy carrier due to its high combustion energy and the generation of water as the sole byproduct. However, the use of Hydrogen gas requires strict supervision as the gas is flammable and explosive at concentrations above 4% in air.
Among various Hydrogen gas sensing materials, palladium (Pd) is known to be very appealing not only for its simple mechanism of change in electrical resistance by reacting with the Hydrogen gas, but also very stable as there are no byproducts during the reaction. However, when Pd is exposed to over over 2% H2 concentration, phase transition occurs which results in limitations of concentration range for detection, delay in reaction time, and impairment of durability, and does not meet the basic requirements of being able to detect H2 concentrations of up to 4%.
To solve this issue, the research team designed and manufactured a new Pd nanostructure in which the chemical potential can be reduced that leads to a lower free energy of phase transition. The new sensor was successfully able to detect H2 concentrations of 0.1~4% with 98.9% linearity. The team also demonstrated a sensor system that wirelessly detects H2 through by incorporating the sensor with BLE (Bluetooth low energy), 3D printing, and an Android application, and it was able to reliably detect H2 leakage with a smartphone or a PC even when located 20 meters away from the sensor. This research is significant in that it was a successful attempt at building a reliable Pd-based H2 sensor that can detect H2 concentrations of over 2%, which was previously difficult to produce. In particular, it is expected that this sensor will be used for safety management in the future where Hydrogen-based clean energy is prevalent. 
Korean newpapers share this news 28th June.
[Relate  link]
 Et News: https://www.etnews.com/20220628000128 
 News 1: https://www.news1.kr/articles/?4725281
 Energy economics: https://www.ekn.kr/web/view.php?key=20220628010004336

EE Prof. Kim, SangHyeon’s team, develops display using 3D integration techniques, promising applications on next generation displays

EE Prof. Kim, SangHyeon’s team, develops display using 3D integration techniques, promising applications on next generation high resolution displays


[ Prof. Kim, SangHyeon, Ju Hyeok Park (P.H.D candidate), Dr. Dae-myeong Geum, Woo Jin Baek (P.H.D candidate), From left]


KAIST EE Prof. Kim, SangHyeon’s research team has successfully developed a 1600-PPI MicroLED display by utilizing monolithic 3D integration techniques, as announced.

(*monolithic 3D integration: dubbed the ultimate 3D integration tech, wherein after the lower-layer devices, the upper layer’s thin film is created and stacking proceeds sequentially so as to maximize the upper-lower device alignment)

(* PPI: pixels per inch)


KAIST EE Prof. Kim, SangHyeon Kim’s research team members Ju Hyeok Park and Dr. Dae-myeong Geum led the work as co-first authors, collaborating with Woo Jin Baek from the same research lab and Dr. Johnson Shieh from Jasper Display in Taiwan. Their joint work has been presented at the “semiconductor Olympics”, the 2022 IEEE Symposium on VLSI Technology & Circuits. (Paper: Monolithic 3D sequential integration realizing 1600-PPI red micro-LED display on Si CMOS driver IC)

MicroLED devices using inorganic-based III-V compound semiconductors are gaining attention as core candidates for next-generation ultra-high resolution displays that are growing rapidly in demand. MicroLEDs offer advantages over current OLED and LCD displays widely used in modern TVs and mobile devices with features such as high luminance and contrast ratio, and a longer pixel life.

(*III-V compound semiconductors: Semiconductors comprising of compounds of Group III and Group V elements in the periodic table, offering excellent charge transport and light characteristics)


A monolithic 3D integration of red light-emitting LEDs on a Si CMOS circuit board was applied to solve the issues present in existing device technology. A demonstration of high-resolution display was made successful through continuous semiconductor processes on the wafer. Through this process, the LED semiconductor display layer was designed to reduce the thickness of the active layer for light emission to 1/3 and greatly reduce the challenges of the etching process required for pixel formation. In addition, to prevent performance degradation of the lower display driving circuit, the research team was able to maintain the performance of the lower Driver IC even after the integration of the upper layer by using ultra-low temperature processes such as wafer bonding that integrates the upper III-V layer below 350 C.

By successfully implementing state-of-the-art resolution of 1600-PPI MicroLED display using a monolithic 3D integration of red LEDs, this result is expected pave way for the next-generation ultra-high resolution displays.

Image 1.


Image 2.

EE Professor Kim, SangHyeon’s team develop 3D Stackable Quantum Computing Readout Device

Title:  EE Professor Kim, SangHyeon’s Research Team Develops 3D Stackable Quantum Computing Readout Device

KAIST Builds 3D Stackable Quantum Computing Readout Device  Low-power, low-noise, high-speed device integrated in 3D operates at super-low temperatures and promises large-scale applications to quantum computing devices.

<(From left) EE Prof. Kim, SangHyeon, PhD candidate Jeong, Jae Yong, NanoFab PhD candidate Kim, Jongmin, and KBSI Prof. Park, Seung-Young>


KAIST EE Prof. Kim, SangHyeon’s research team has developed a 3D-stacked semiconductor readout device integration technology, as made public on the 16th. The team made this possible by applying the strengths of monolithic 3D integration to overcome large-scale qubit implementation based on existing quantum computing systems. Their work is a first of its kind exhibiting the 3D stackability of quantum computing readout devices after an actively pursued line of research on monolithic 3D stacking of high-speed devices following a 2021 VLSI presentation, a 2021 IEDM presentation, and a 2022 ACS Nano publication.

(*monolithic 3D integration: dubbed the ultimate 3D integration tech, wherein after the lower-layer devices, the upper layer’s thin film is created and stacking proceeds sequentially so as to maximize the upper-lower device alignment)

KAIST EE Prof. Kim, SangHyeon Kim’s research team member Jeong, Jae Yong led the work as first author, collaborating with NanoFab PhD candidate Kim, Jongmin and KBSI Prof. Park, Seung-Young. Their joint work has been presented at the “semiconductor Olympics”, Symposium on VLSI Technology. (Paper: 3D stackable cryogenic InGaAs HEMTs for heterogeneous and monolithic 3D integrated highly scalable quantum computing system)

A qubit is capable of processing twice the amount computation compared with that of a bit. Number of qubits increasing linearly results in exponential speedup of their computation. Thus, developing large-scale quantum computing is of utmost importance. IBM, for instance, presented Eagle containing 127 qubits, and the IBM roadmap outlines development of a 4,000-qubit quantum computer by 2025 and one with 10,000-qubits or more in 10 years.

Designing such large-scale quantum computers with many qubits requires implementing devices for qubit control/readout. The research team has not only proposed and implemented 3D-stacked control/readout devices but also achieved world-best cutoff frequency characteristics at cryogenic settings despite the 3D stacking.

This work has been supported by the National Research Foundation of Korea, the System Semiconductor Development Program funded by Gyeonggi-do, and the Korea Basic Science Institute.