Jun Hee Lee Email & Phone Number

Evanston, Illinois, United States

Dedicated to investigating ultra-wide bandgap semiconductors, with a primary focus on novel metal oxides (i.e. Ga2O3) and a secondary interest in III-Nitrides (i.e. AlN, AlGaN, GaN) using epitaxial growth techniques, particularly metalorganic chemical vapor deposition (MOCVD). (a)Conceptualization and Method Developments to produce High-quality Epitaxial Ga2O3 Films•Examined and analyzed the effects of MOCVD growth parameters such as growth temperature, pressure and different precursors to produce epitaxial Ga2O3 layers with low defect density; Introduced novel techniques, including Ga pre-deposition, the usage of indium as an effective surfactant, and the incorporation of β-Ga2O3 buffer layer to mitigate defect formation during MOCVD growth.(b)Direct Epitaxial Synthesis of Ga2O3/III-Nitrides Heterostructures •Introduced AlOx interlayer method to facilitate the epitaxial growth of Ga2O3/III-Nitride heterostructures, overcoming the challenge of large lattice mismatch between the two material systems and effectively addressing the poor heat conductivity of Ga2O3. (c)Investigation on the Chemical Dynamics in the course of Epitaxial Ga2O3 Growth •Explored and assessed the influence of hydrogen (H2) and nitrogen (N2) on MOCVD-grown Ga2O3 epilayers; The quantity of H2 plays a pivotal role in determining both the quality and polymorph of Ga2O3, while the presence of N2 induces p-type conductivity in Ga2O3 as a dopant. (d)Evaluation and Analysis of Epitaxial Layers through Various Characterization Techniques •Investigated and analyzed MOCVD-grown epilayers through comprehensive structural, optical, and electrical characterization measurement techniques including Atomic Force Microscope (AFM), Scanning Electron Microscope (SEM), High resolution X-ray Diffraction (HR-XRD), Energy-dispersive X-ray spectroscopy (EDX), Photoluminescence (PL), Optical Transmission Measurement, Hall Effect Measurement.

(a)Device Fabrication and Characterization in Opto-/Electronic Devices •Engineered opto-/electronic devices, such as Metal-Semiconductor-Metal (MSM) diodes, PN diodes, and transistors and conducted comprehensive analyses of device characteristics, including output and transfer IV curves, as well as responsivity measurements.

Dedicated to optimizing the performance of fabricated electronic devices, particularly thin-film transistors (TFTs), utilizing metal oxide semiconductors such as In2O3, ZnO, and IGZO. Deposition methods primarily involved the solution process, occasionally via sputtering. (a)Surface Oxidation Investigation during Annealing Process for Material Quality Enhancement •Identified surface oxidation phenomenon during annealing process as an effective method for eliminating various defects, particularly within the top 5 nm of thin films. This observation led to the development of high-quality metal oxide thin films with superior electrical properties. (b)Fabrication and Optimization of High-Performance Metal Oxide TFTs•Designed new TFT arrays and mesa structure using AutoCAD to enhance the performance of semiconductor devices. Systematically optimized critical steps in the semiconductor device fabrication processes including photolithography, patterning, wet etching, and lift-off procedure. (c)Evaluation and Analysis of Materials and Devices through Various Characterization Techniques•Estimated the quality of metal oxide thin films through comprehensive characterization measurement techniques including AFM, Grazing Incidence XRD (GI-XRD), X-ray Reflectometry (XRR) and X-ray Photoelectron Spectroscopy (XPS); Executed a diverse array of electrical performance measurements on TFTs and basic logic gate inverters, encompassing output and transfer IV curves, as well as CV measurements.

(a)Investigation in impacts of Atmosphere Plasma Treatment•Provided support to examine effects of Atmosphere Plasma Treatment on solution-processed metal oxide thin-film transistors Publication: (1) Effective Atmospheric-Pressure Plasma Treatment toward High-Performance Solution-Processed Oxide Thin-Film Transistors, ACS Appl. Mater. Interfaces 2018, 10, 36, 30581–30586(2) Atmospheric-pressure plasma treatment toward high-quality solution-processed aluminum oxide gate dielectric films in thin-film transistors, Nanotechnology 2019, 30, 495702(b) Developing precursors for solution-grown electronics of few defects •Assisted to form various types of precursors and provided support in the synthesis of dataPublication: A systematic study on effects of precursors and solvents for optimization of solution-processed oxide semiconductor thin-film transistors, J. Mater. Chem. C, 2017, 5, 7768-7776

(a)Modeling new type of Non-Volatile Memory•Assisted the research project on modeling of metal oxide-resistive memory (RRAM/ReRAM) using graphene-edge electrodes•Analyzed electrical characteristics of the RRAM with graphene-edge electrodes and contributed to developing electrical characteristic equations(b)Designing MIPS CPU for improved operation •Designed Microprocessor without Interlocked Pipeline Stages Center Processing Unit (MIPS CPU) with enhanced branch predictor and performed from Front End to Place and Route of Back End

• Developed strong interpersonal and communication skills through daily interactions with diverse groups• Demonstrated leadership as a squad leader, supervising a team of 13 soldiers• Conducted various tasks and received awards/recognition for outstanding performance while leading the team

Doctor Of Philosophy - Phd, Electrical Engineering

Master'S Degree, Nano Science And Technology

Bachelor'S Degree, Electronics And Radio Engineering

Exchange Student, Communication And Media Studies