https://scholar.gist.ac.kr/handle/local/7920 2026-01-30T23:02:13Z 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. 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. 2025-09-30T15:00:00Z 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. 2016-12-31T15:00:00Z https://scholar.gist.ac.kr/handle/local/9483 Title: Understanding the Growth Mechanisms of γ-GeSe for Polymorph-Selective Large-Area Deposition Author(s): Jung, Joong-Eon; Lee, Sol; Kang, Hani; Jang, Myeongjin; Park, Jinsub; Petri, Mustonen; Lipsanen, Harri; Sun, Zhipei; Yoon, Hoon Hahn; Kim, Kwanpyo Abstract: Understanding the growth mechanisms of a newly discovered polymorphic material and achieving large-scale selective growth is critical for accurate material characterization and application. Post-transition metal monochalcogenides, including Ge chalcogenides, are known to exhibit various polymorphic configurations, and selectively growing a target metastable polymorph is challenging. This study delves into the growth mechanisms and polymorph-selective growth methods of gamma-phase germanium selenide (GeSe), a recently identified hexagonal polymorph. The role of the Au catalyst in the vapor-liquid-solid synthesis of gamma-GeSe is investigated in detail via crystallographic and morphological investigations of growth products as a function of Au catalyst size. Azimuthally-aligned gamma-GeSe flakes grow more efficiently and selectively on boron nitride and graphite templates, indicating the importance of the growth substrate. Chemical-vapor-deposited graphene-covered substrates allow for large-area growth of gamma-GeSe, leading to practical applications.,This work unveils the pivotal roles of Au catalysts and substrates in the polymorph-selective, large-area synthesis of gamma-GeSe. The demonstrated synthesis of gamma-GeSe will advance energy storage and optoelectronics applications with the new polymorph., 2024-06-30T15:00:00Z