Research

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*RESEARCH AREA*

- Compound semiconductor (GaN, Ga₂O₃, ZnO, La₂O₃) based gas sensor

- Oxide (ZnO, CdO, MgO) based light emitting diode (LED)

- Nanostructure materials including Pt, Pd, Au, Ag, ZnO, and La₂O₃

*RESEARCH INTERESTS*

Our research interests include nitride and oxide semiconducor based sensors, light emitting diodes, and integrated electronic devices using nanostructure materials.

- Wide bandgap semiconductors including GaN, Ga₂O₃, and ZnO are very suitable materials for constructing gas sensor. The wide bandgap and radiation hardness guarantee the high signal to noise ratio of the sensor in addition to stable operation of the device at high temperature and in harsh radiative environment. Especially, the mechanical and chemical robustness of GaN ensure great sensing reliability and durability.

- Complicate and high-cost metal organic chemical vapor deposition (MOCVD) grown nitride based materials such as GaN, InGaN, and AlGaN are commercially used as epitaxial layers of blue and UV LED in applications of display and lighting sources. ZnO is a promising light emitting material with wide bandgap energy of 3.37 eV and larger exciton binding energy of 60 meV than 28 meV for GaN at room temperature. One of the advantages of ZnO is facile growth method via hydrothermal growth, which is low cost, non-toxic, low temperature, and scalable process.

*RESEARCH ACTIVITY HIGHLIGHTS*

- 94 technical published papers in referred journals
- 25 contributed and 9 invited international conference presentations
- List of Technical Achievements

2019.05. Investigation of hydrogen responsivity on ZnO crystal planes

2018.01. Investigation on wet etching and contacts on (-201) and (010) β-Ga₂O₃

2017.11. Development of nonpolar light emitting diode with hydrothermally grown a-plane ZnCdO on p-GaN

2017.11. Investigation on Ohmic contact properties of nonpolar m-plane GaN

2017.07. Development of ethanol sensor based on AlGaN/GaN HEMT with catalytic silver

2017.06. Investigation on Ohmic contact properties of photo-chemically etched a-plane GaN

2017.05. Development of carbon dioxide sensor based on AlGaN/GaN HEMT with ZnO nanorods on gate region

2017.04. Development of highly sensitive ammonia sensor based on AlGaN/GaN HEMT with ZnO nanorods on gate region

2017.01. Development of AlGaN/GaN HEMT hydrogen sensor with PMMA or polyimide based moisture barrier for humid and high temperature ambient application.

2016.06. Development of highly sensitive hydrogen diode sensors based on (11-20) and (11-22) plane GaNs using photo-chemical etching

2016.01. Development of hydrogen sensitive Schottky diode using semipolar (11-22) AlGaN/GaN heterostructure

2015.01. Investigation on hydrothermal growth of a-plane ZnO using epitaxial lateral overgrowth

2014.05. Investigation of hydrogen sensing characteristics depending on GaN crystal planes including (0001), (000-1), (11-20) and (11-22)

2013.10. Investigation of carrier transport properties in semipolar (11-22) GaN films with low defect density

2013. 8. Development of nonpolar light emitting diode with sharp near-ultraviolet emissions using hydrothermally grown a-plane ZnO on p-GaN

2012. 9. Development of improved organic light emitting diodes using cryogenic LiF/Al electrodes

2012. 3. Development of highly sensitive AlGaN/GaN HEMT-based hydrogen sensors using platinum nanonetworks

2011. 7. Investigation of neutron irradiation on AlGaN/GaN high electron mobility transistors on SiC substrates

2011. 3. Investigation of electric-field-driven degradation in off-state step-stressed AlGaN/GaN high electron mobility transistors

2010. 9. Investigation of reverse gate bias-induced degradation for AlGaN/GaN high electron mobility transistors

2010. 7. Investigation of hydrogen sensing characteristics for non-polar a-plane GaN Schottky diodes

2010. 7. Investigation of ohmic contact properties for non-polar a-plane GaN films on r-plane sapphire substrates

2009. 1. Development of 32 Gb NAND flash memory using 35 nm technology

2008. 3. Development of 16 Gb NAND flash memory using 51 nm technology

2007. 1. Design of Transparent Indium Tin Oxide Based Inter-Digitated Fingers for Metal Semiconductor Metal Photodetector

2006. 3. Simulation of vertical and lateral ZnO light-emitting diodes

2005. 11. Development of Si-Diffused GaN for Enhancement-Mode GaN MOSFET on Si

2005. 11. Formation of p-n homojunctions in n-ZnO bulk single crystals by diffusion from a Zn₃P₂ source

*CONFERENCE PRESENTATIONS (International)*

1. (Invited) Compound semiconductor based Gas sensors, 2019 International Conference on Smart Sensors, Hsinchu, Taiwan, June 3^rd, 2019
2. Hydrogen sensors for high temperature and humid environment applications, 235nd Electrochemical Society Meeting, Dallas, U.S.A. May 18^th, 2019
3. Sensitivity Enhancement Technologies for Black Phosphorous-based Gas sensors, 223nd Electrochemical Society Meeting, Seattle. U.S.A. May 16^th, 2018
4. Encapsulation of AlGaN/GaN High Electron Mobility Transistor based Hydrogen Sensor for Humid Ambient Sensing Application, 64^th American Vacuum Society International Symposium & Exhibitions, Tampa, U.S.A. October 30^th, 2017
5. (Invited) Advances in Ga₂O₃ Processing and Devices, 232nd Electrochemical Society Meeting, National Harbor, U.S.A. October 2nd, 2017
6. Highly sensitive GaN based hydrogen sensors using nanostructure sensing materials, 43rd International Conference on Micro and Nanoengineering, Baraga, Portugal, September 21st, 2017
7. GaN based hydrogen sensor in humid ambient, 231th Electrochemical Society Meeting, New Orleans, U.S.A. May 29th, 2017
8. GaN based Carbon Dioxide Sensor, 231th Electrochemical Society Meeting, New Orleans, U.S.A. May 30th, 2017
9. The birefringence study of nonpolar a-plane GaN films using terahertz time-domain spectroscopy, 231th Electrochemical Society Meeting, New Orleans, U.S.A. May 30th, 2017
10. (Invited) Hydrogen sensing characteristics of highly sensitive and reliable GaN based gas sensor, 41st International conference and exposition on advanced ceramics and composites, Daytona beach, U.S.A., January 24^th, 2017
11. GaN based Ethanol Sensor, 230th Electrochemical Society Meeting, Honolulu, U.S.A. October 5^th, 2016
12. (Invited) Improved GaN based Hydrogen Sensors, 229th Electrochemical Society Meeting, San Diego, U.S.A, June 3^th, 2016
13. Hydrogen Sensing Enhancement of Semipolar GaN Schottky Diode Using Photoelectrochemical Wet Etching, International conference on electronics, information, and communication, Danang, Vietnam, Jan. 28^th, 2016
14. Nonpolar ZnO based light emitting diode, 14th international Union of Materials Research Societies-International Conference on Advanced Materials, Jeju, Korea, Oct. 28th, 2015
15. Optical Properties of Nonpolar a-plane ZnO Crystals in the Terahertz Frequency Region, 14th international Union of Materials Research Societies-International Conference on Advanced Materials, Jeju, Korea, Oct. 27^th, 2015
16. Hydrogen Sensitive Schottky Diodes Using Semipolar AlGaN/GaN HEMT Heterostructures, Asia-Pacific Workshop on Fundamentals and applications of Advanced Semiconductor Devices, Jeju, Korea, June 29^th, 2015
17. Hydrothermally Grown Nonpolar a-plane ZnO and Its Applications, 227th Electrochemical Society Meeting, Chicago, U.S.A, May 26^th, 2015
18. Lateral Overgrowth of a-plane Epitaxial ZnO using Hydrothermal Method, International Conference on Electronic Materials and Nanotechnology for Green Energy, Jeju, Korea, Nov. ¹⁷, 2014
19. The Growth Evolution of K-doped ZnO Nanorods by Hydrothermal Growth Method on Semipolar GaN Films, International Conference on Electronic Materials and Nanotechnology for Green Energy, Jeju, Korea, Nov. ¹⁷, 2014
20. (Invited) Nonpolar a-plane ZnO Growth for LEDs, Collaborative Conference on Crystal Growth, Phuket, Thailand, Nov. 5^th, 2014
21. (Invited) Hydrogen Sensing Characteristics of Gallium Nitrides with Various Crystal Planes, 225th Electrochemical Society Meeting, Orlando, U.S.A, May 7th, 2014
22. Nonpolar Light-Emitting Diodes Using Hydrothermally Grown a-Plane ZnO, 224th Electrochemical Society Meeting, San Francisco, U.S.A, Oct. 28th, 2013
23. (Invited) Improved Hydrogen Sensing Performance of AlGaN/GaN based sensor with Platinum Nanonetworks, 222nd Electrochemical Society Meeting, Honolulu, U.S.A, Oct. 8^th, 2012
24. Highly Sensitive Pt Nano-network sensor for Hydrogen Detection in fuel cell vehicle applications, 2012 Energy Materials Nanotechnology Meeting, Orlando, U.S.A., Apr 19^th, 2012
25. Aniosotropies of Nonpolar a-Plane GaN LEDs in Electrical and Optical Properties, 2011 International Conference on Compound Semiconductor Manufacturing Technology, Indian Wells, U.S.A., May 16^th, 2011
26. (Invited) Pt nano-networks for Hydrogen Sensing Applications, 9^th Korea-Japan Symposium on Materials & Interfaces, Yousu, Korea, Oct 31^th, 2010
27. Effect of neutron irradiation in AlGaN/GaN high electron mobility transistor on SiC substrate, 2010 International Conference on Electronic Materials, Ilsan, Korea, Aug 22^th, 2010
28. (Invited) a-Plane GaN for Hydrogen Sensing Applications (Invited), 217th Electrochemical Society Meeting, Vancouver, Canada, Apr 25^th, 2010
29. Compound Semiconductor for Sensing and Optoelectronic Device Application, 3rd International Symposium on Integrated Nano-Bio Materials and Devices, Chunan, Korea, Nov 4^th, 2009
30. Compound Semiconductors for Bio-sensor Application (Invited), 2009 Anual Conference of Institute of Tissue Regeneration Engineering, Chunan, Korea, Apr 30^th, 2009
31. ZnO Light Emitting Diode Simulation, 209^th Electrochemical Society Meeting, Denver, CO, May 9^th, 2006
32. Si-Diffused Enhancement-Mode GaN MOSFET, 72^nd Annual Meeting of the Southeastern Section of the American Physical Society, Gainesville, FL, Nov 12^th, 2005
33. Study of Si Diffused GaN for Enhancement-Mode MOSFET, 47^th Annual TMS Electronic Materials Conference, Santa Barbara CA, Jun 22th, 2005
34. Improved InGaAs Metal-Semiconductor-Metal OE Mixers Using submicron schottky contacts, 24^th Army Science Conference 2004, Orlando FL, Nov 29^th 2004.