Jeonbuk National University (JBNU) Professor Bae Hak-yeol (Division of Electronic Engineering) and University of Seoul Professor Kim Tae-wan (Division of Advanced Convergence) formed a joint research team that has developed an analytical method capable of precisely identifying the causes of damage to next-generation aerospace semiconductors.

The research team was the first to analyze the degradation mechanism that occurs when IGZO, which is applied to next-generation memory, is exposed to gamma rays present in the space environment. They published their paper in the latest issue of the leading journal in the field, Advanced Electronic Materials (Link: https://onlinelibrary.wiley.com/doi/10.1002/aelm.202300906).

IGZO is a metal oxide material composed of indium (In), gallium (Ga), and zinc oxide (ZnO). It can be fabricated without large-area capacitors, improving device integration density and yield. IGZO also exhibits low leakage current and relatively high mobility, which has attracted attention as a next-generation memory material.

Gamma rays are emitted as electromagnetic radiation from radioactive decay of atomic nuclei. Exposure to gamma rays is likely in aviation, military, medical devices, and space applications. Therefore, analyzing degradation mechanisms under gamma-ray exposure is crucial for ensuring that next-generation memories perform reliably in such harsh environments.

To this end, the research team developed a method to characterize the density of states (DOS) within the energy bandgap using light sources of specific wavelength bands. Oxide semiconductors commonly have defects known as oxygen vacancies within the bandgap. The team quantitatively assessed the amount of such defects by investigating various light sources with photon energies smaller than IGZO's bandgap.

This technique used current–voltage (I–V) measurement analysis and offers the advantage of being applicable not only to oxide semiconductors but also to various semiconductor materials and microdevices such as silicon, 2D-channel materials, and graphene.

In addition, the team observed changes in the density of states across the entire bandgap region using the optical–electrical nondestructive analysis method introduced in this study. 

After radiation exposure, an increase in oxygen-vacancy-related defects at specific energy levels within the bandgap was observed. This phenomenon causes critical instabilities in device threshold voltage and switching characteristics. The experimental results were validated by X-ray photoelectron spectroscopy (XPS), which can analyze physicochemical information such as constituent elements, composition ratios, and chemical bonding states.

IGZO, noted as a next-generation memory material, can be applied across multiple fields. High levels of device reliability are therefore required, and because devices are likely to operate in radiation-exposed environments, analysis of this kind is important. The research results are expected to have high application value.

Professor Bae said, "Through this research, we have developed a precise analytical method capable of identifying the causes of radiation-induced damage in aerospace semiconductors," and added, "We will develop semiconductor materials and devices with high radiation tolerance to enhance technological maturity."

Meanwhile, this research was carried out with support from the National Research Foundation of Korea's Basic Research program and JBNU's 4th-phase BK21 JIANT-IT Human Resources Development Project Division.