A research team led by Professor Kwangwook Park in the Major of Electronic Materials Engineering at Jeonbuk National University (JBNU) has identified the cause of electrical property degradation with increasing thickness in ZnSnN₂ thin films, a low-cost next-generation nitride semiconductor.

This study was carried out jointly by Professor Kwangwook Park and doctoral student Juchan Hwang from the Major of Electronic Materials Engineering at JBNU, and Senior Researcher Cheol Kang and Researcher Youngil Kim of the Advanced Photonics Research Institute (APRI) at the Gwangju Institute of Science and Technology.

ZnSnN₂ is a II–IV–N₂ family nitride semiconductor that uses abundant and relatively inexpensive Zn and Sn. It has attracted attention as a next-generation, low-cost semiconductor material that could complement existing III–N compound semiconductors such as GaN. In particular, its potential for visible-band applications is large, raising expectations for expansion into devices such as photodetectors, solar cells, and optoelectronic components.

Professor Kwangwook Park's team grew ZnSnN₂ thin films using sputter deposition, which offers greater industrial scalability than costly methods such as MBE or MOCVD, and analyzed the causes of electrical property degradation as a function of growth time. Sputter-grown ZnSnN₂ films develop a vertical columnar structure, but as film thickness increased, carrier mobility and electrical conductivity decreased.

The research team used Hall measurements and terahertz time-domain spectroscopy (THz-TDS) to distinguish whether this phenomenon was due to intrinsic degradation of ZnSnN₂ material properties or to microstructural changes. The results showed that while the macroscopic electrical transport properties of the entire film were markedly degraded, the local electrical response within individual columns was largely preserved.

Electron microscopy and diffraction analyses confirmed that with longer growth times the column width and column tilt increased and intercolumnar voids formed. This indicates that the degradation of electrical properties in thick ZnSnN₂ films is caused more by intercolumnar voids and reduced connectivity between columns than by deterioration of properties within individual columns.

Professor Kwangwook Park stated, "This study shows that in sputter-grown ZnSnN₂ films the cause of electrical property degradation is not intrinsic material degradation but decreased connectivity between columns," and added, "To utilize low-cost nitride semiconductors in practical devices, it is necessary to control not only composition but also microstructure and charge transport pathways."

Meanwhile, this research was conducted with support from JBNU's 2025 National University Development Project support program for the implementation of strategic research specialization by priority fields, and the results were published in the international journal Journal of Materials Chemistry C, published by the Royal Society of Chemistry, under the title "Consistent Evidence for Intra- and Inter-Columnar Transport Decoupling in Sputter-Grown ZnSnN₂ Thin Films through Growth-Driven Microstructural Evolution" (DOI: 10.1039/d6tc01289b).