Young-Jun Yu

Photodoping plays an important role in determining the optoelectronic response of 2D semiconductor devices; however, the origin of the responsible trap states remains unclear. In this work, we investigate UV-induced photodoping in multilayer WSe2 field-effect transistors (FETs) based on WSe2/hBN heterostructures on SiO2/p-Si substrates. Wavelength-dependent measurements reveal pronounced n-type photodoping under 405 nm illumination, whereas the effect is orders of magnitude weaker under 640 nm excitation and for p-type photodoping. Furthermore, when the SiO2 layer is removed, both n-type and p-type photodoping are strongly suppressed, demonstrating that the oxide layer is essential for persistent photodoping. Analysis of defect-state distributions in amorphous SiO2, together with first-principles calculations for hBN defects, shows that the experimental observations cannot be explained by defects in hBN. Instead, the results indicate that defect states in the SiO2 substrate act as charge reservoirs that facilitate charge transfer and long-term carrier trapping. These findings highlight the dominant role of substrate-related trap states in UV-induced photodoping and photogating behavior in WSe2 FET devices.

Oh Hun Gwon, Kyu Yeon Kim, Hye Ryung Byun, Il-Wook Cho, Muntae Hwang, Mee-Yi Ryu, and Young-Jun Yu. Applied Science and Convergence Technology 2026;35:72-5. https://doi.org/10.5757/ASCT.2026.35.2.72

Beomkyu Shin, Yeonwoo Choi, Jong Yun Kim, Ji-Hyun Cha, and Young-Jun Yu. Applied Science and Convergence Technology 2024;33:104-7. https://doi.org/10.5757/ASCT.2024.33.4.104

Seo Gyun Jang, Oh Hun Gwon, BeomKyu Shin, Daehyun Ryu, and Young-Jun Yu. Applied Science and Convergence Technology 2024;33:50-2. https://doi.org/10.5757/ASCT.2024.33.2.50

α‐In₂Se₃ semiconductor crystals realize artificial synapses by tuning in‐plane and out‐of‐plane ferroelectricity with diverse avenues of electrical and optical pulses. While the electrically induced ferroelectricity of α‐In₂Se₃ shows synaptic memory operation, the optically assisted synaptic plasticity in α‐In₂Se₃ has also been preferred for polarization flipping enhancement. Here, the synaptic memory behavior of α‐In₂Se₃ is demonstrated by applying electrical gate voltages under white light. As a result, the induced internal electric field is identified at a polarization flipped conductance channel in α‐In₂Se₃/hexagonal boron nitride (hBN) heterostructure ferroelectric field effect transistors (FeFETs) under white light and discuss the contribution of this built‐in electric field on synapse characterization. The biased dipoles in α‐In₂Se₃ toward potentiation polarization direction by an enhanced internal built‐in electric field under illumination of white light lead to improvement of linearity for long‐term depression curves with proper electric spikes. Consequently, upon applying appropriate electric spikes to α‐In₂Se₃/hBN FeFETs with illuminating white light, the recognition accuracy values significantly through the artificial learning simulation is elevated for discriminating hand‐written digit number images.

Oh Hun Gwon, Seo Gyun Jang, Jong Yun Kim, Han Seul Kim, and Young-Jun Yu. Applied Science and Convergence Technology 2022;31:110-2. https://doi.org/10.5757/ASCT.2022.31.5.110