https://scholar.gist.ac.kr/handle/local/7920 Thu, 06 Aug 2026 23:24:25 GMT 2026-08-06T23:24:25Z https://scholar.gist.ac.kr/handle/local/15699 Title: ZnO/p-GaN Heterostructure for Solar Cells and the Effect of ZnGa2O4 Interlayer on Their Performance Author(s): Nam, Seung Yong; Choi, Yong Seok; Lee, Ju Ho; Park, Seong-Ju; Lee, Jeong Yong; Lee, Dong-Seon Abstract: We report the usage of ZnO material as an alternative for n-GaN for realizing III-nitride based solar cell. The fabricated solar cell shows large turn-on voltage of around 8 volts and a rapid decrease of photocurrent at low bias voltage under darkness and 1-sun illumination conditions, respectively. This phenomenon can be attributed to the formation of high-resistive ultra-thin layers at the ZnO/p-GaN junction interface during high temperature deposition. Transmission electron microscopy (TEM) studies carried out on the grown samples reveals that the ultra-thin layer consists of ZnGa2O4. It is found that the presence of insulating ZnGa2O4 film is detrimental in the performance of proposed heterostructure for solar cells. Mon, 31 Dec 2012 15:00:00 GMT https://scholar.gist.ac.kr/handle/local/15699 2012-12-31T15:00:00Z https://scholar.gist.ac.kr/handle/local/32211 Title: Wafer-scale fabrication of memristive passive crossbar circuits for brain-scale neuromorphic computing Author(s): Choi, Sanghyeon; Bezugam, Sai Sukruth; Bhattacharya, Tinish; Kwon, Dongseok; Strukov, Dmitri B. Abstract: Memristive passive crossbar circuits hold great promise for neuromorphic computing, offering high integration density combined with massively parallel operation. However, scaling up the integration complexity of such circuits remains challenging due to low device yield, stemming from the intrinsic properties of filamentary switching and limitations in current crossbar fabrication technologies. Here, we report a scalable passive crossbar device technology achieved through a co-design approach for memristors and crossbar structures. The proposed hardware platform is fabricated using CMOS-compatible processes without complex and high-temperature steps, enabling high device yield along with reliable and multibit operation. Importantly, the fabrication process is successfully scaled to a 4-inch wafer, maintaining an average device yield (>similar to 95%) and preserving key switching characteristics. The potential of this platform is showcased by implementing image classification of the fashion MNIST benchmark with an ex-situ trained spiking neural network. We believe that our work represents a significant step toward brain-scale neuromorphic computing systems. Tue, 30 Sep 2025 15:00:00 GMT https://scholar.gist.ac.kr/handle/local/32211 2025-09-30T15:00:00Z https://scholar.gist.ac.kr/handle/local/33620 Title: Wafer-Bonded AlGaInP Red LEDs with Suppressed S-Droop through Surface Sulfidation Author(s): Lee, Je-Sung; Mun, Seung-Hyun; Shin, Sunwoo; Kim, Rae-Young; Lee, Seung Hyeok; Cha, Sugyeong; Han, Hye-Sung; Kim, Kyung-Pil; Kwak, Hoe-Min; Baik, Jaeyoung; Choi, Soo-Young; Kim, Sang-Jo; Jeong, Woo-Lim; Kim, Jun-Youn; Jo, Sung-Chan; Kang, Chang-Mo; Lee, Dong-Seon Abstract: Micro-light-emitting diode (micro-LED) technology enables high pixels-per-inch (PPI) displays using conventional semiconductor processes and relies on extremely miniaturized mesa structures derived from traditional LEDs. Scaling to smaller sizes leads to a significant decrease in emission efficiency because of the stronger influence of sidewall damage. This efficiency degradation, known as the size-effect or S-droop, primarily arises from surface defects introduced by dry etching. These defects promote nonradiative Shockley-Read-Hall (SRH) recombination and create pathways for surface leakage current. In aluminum gallium indium phosphide (AlGaInP) LEDs, chemical passivation with ammonium sulfide is widely used to mitigate sidewall damage. However, the underlying reaction mechanism remains unclear, and most studies address only the sidewall regions. In this work, we fabricated a wafer-bonded vertical AlGaInP LED structure compatible with light-emitting diode on silicon (LEDoS) integration and applied ammonium sulfide surface sulfidation to investigate its broader effects. Chemical changes from sulfidation were examined using energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). These analyses revealed that surface defects were replaced by stable sulfur bridge bonds, leading to Fermi level unpinning. Electrical characterization further separated parallel and series resistances, which revealed the influence of surface sulfidation across both the top and sidewall interfaces. As a result, the maximum external quantum efficiency (EQE) increased by 120.6% at 5 A/cm2 in a 10 mu m pixel, accompanied by a clear reduction in S-droop. Sat, 31 Jan 2026 15:00:00 GMT https://scholar.gist.ac.kr/handle/local/33620 2026-01-31T15:00:00Z https://scholar.gist.ac.kr/handle/local/13936 Title: Very thin ITO/metal mesh hybrid films for a high-performance transparent conductive layer in GaN-based light-emitting diodes Author(s): Min, Jung-Hong; Kwak, Hoe-Min; Kim, Kiyoung; Jeong, Woo-Lim; Lee, Dong-Seon Abstract: In this paper, we introduce very thin Indium tin oxide (ITO) layers (5, 10, and 15 nm) hybridized with a metal mesh to produce high-performance transparent conductive layers (TCLs) in near-ultraviolet light-emitting diodes (NUV LEDs). Using UV-vis-IR spectrometry, Hall measurement, and atomic force microscopy, we found that 10 nm was the optimal thickness for the very thin ITO layers in terms of outstanding transmittance and sheet resistance values as well as stable contact properties when hybridized with the metal mesh. The proposed layers showed a value of 4.56 Omega/square, for sheet resistance and a value of 89.1% for transmittance. Moreover, the NUV LEDs fabricated with the hybrid TCLs achieved similar to 140% enhanced light output power compared to that of 150 nm thick ITO layers. Finally, to verify the practical usage of the TCLs for industrial applications, we packaged the NUV LED chips and obtained improved turn-on voltage (3.48 V) and light output power (similar to 116%) performance. Sat, 31 Dec 2016 15:00:00 GMT https://scholar.gist.ac.kr/handle/local/13936 2016-12-31T15:00:00Z