Pohang University of Science and Technology · Engineering
Professor Byoung Hun Lee's research lab specializes in advanced semiconductor materials and devices, with a primary focus on high-κ dielectrics, ultra-thin oxide films, and novel gate stack architectures for next-generation CMOS transistors. The lab investigates the physical, electrical, and reliability properties of materials such as HfO₂ and TiO₂, emphasizing atomic-scale interface engineering, dielectric scaling, and thermal stability. It also explores emerging applications in flexible and transparent electronics, including graphene-based transparent electrodes for organic solar cells and high-performance photodetectors using graphene-silicon heterojunctions. The lab’s work bridges fundamental materials science with practical device integration for energy-efficient and high-performance electronics.
Figures are computed from collected data and may differ slightly.
Dielectric properties of ultrathin hafnium oxide reoxidized with rapid thermal annealing (RTA) have been investigated. Capacitance equivalent oxide thickness (CET) of 45 Å hafnium oxide was scaled down to ∼10 Å with a leakage current less than 3×10−2 A/cm2 at −1.5 V (i.e., ∼2 V below VFB). Leakage current increase due to crystallization was not observed even after 900 °C rapid thermal annealing (RTA), but CET did increase after high temperature RTA due to the interfacial layer growth and possibl
Scaling of the gate stack has been a key to enhancing the performance of complementary metal-oxide-semiconductor (CMOS) field-effect transistors (FETs) of past technology generations. Because the rate of gate stack scaling has diminished in recent years, the motivation for alternative gate stacks or novel device structures has increased considerably. Intense research during the last decade has led to the development of high dielectric constant (k) gate stacks that match the performance of conven
Physical, electrical and reliability characteristics of ultra thin HfO/sub 2/ as an alternative gate dielectric were studied for the first time. Crucial process parameters of oxygen modulated dc magnetron sputtering were optimized to achieve an equivalent oxide thickness (EOT) of 11.5 /spl Aring/ without deducting the quantum mechanical effect. Leakage current was 3/spl times/10/sup -2/ A/cm/sup 2/ at +1 V. Excellent dielectric properties such as high dielectric constant, low leakage current, go
Flexible organic solar cells (OSCs) composed of blended films of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) were fabricated and investigated with chemically doped multilayer graphene films as transparent and conducting electrodes on plastic substrates. The sheet resistance of the chemically doped graphene film was reduced to half of its original value, resulting in a significant performance enhancement of OSCs featuring doped graphene electrodes. Moreover
Effects of interfacial layer growth on reactively sputter-deposited TiO2 films were studied. Leakage current was reduced to 10−8 A/cm2 at +1 V after annealing in oxygen ambient and showed tunneling-like temperature dependence. As the interfacial layer grew, interface states and hysteresis were improved significantly. However, the reliability was degraded as the annealing temperature increased.
Various photodetectors showing extremely high photoresponsivity have been frequently reported, but many of these photodetectors could not avoid the simultaneous amplification of dark current. A gate-controlled graphene-silicon Schottky junction photodetector that exhibits a high on/off photoswitching ratio (≈10<sup>4</sup> ), a very high photoresponsivity (≈70 A W<sup>-1</sup> ), and a low dark current in the order of µA cm<sup>-2</sup> in a wide wavelength range (395-850 nm) is demonstrated. Th
Abstract A high‐responsivity near‐infrared photodetector is demonstrated using a transparent ZnO top gate‐modulated graphene/Ge Schottky junction. The responsivity of a graphene/Ge junction photodetector characterized with a scanning photocurrent microscopy system is improved to 0.75 A W −1 . This result is 5 to 35 times higher than the previously reported graphene/Ge photodetectors that did not use gate modulation. The detectivity is also improved to 2.53 × 10 9 cm Hz 1/2 W −1 at V g = −10 V fr
Abstract The performance of a graphene/Ge Schottky junction near‐infrared photodetector is significantly enhanced by inserting a thin Al 2 O 3 interfacial layer between graphene and Ge. Dark current is reduced by two orders of magnitudes, and the specific detectivity is improved to 1.9 × 10 10 cm ⋅ Hz 1/2 W −1 . The responsivity is improved to 1.2 AW −1 with an interfacial layer from 0.5 AW −1 of the reference devices. The normalized photo‐to‐dark current ratio is improved to 4.3 × 10 7 W −1 at
High- <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</i> dielectrics have been intensively investigated during the last decade, and their performance as a gate dielectric has been improved to the level of conventional SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -based gate dielectric at an equivalent oxide thickness (EOT) ~1 nm. The understanding on metal electrodes and their interactio
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