The operational principles and governing laws of the "charge trap" phenomenon in amorphous semiconductors, which had remained an unresolved problem for over 40 years, have been elucidated for the first time. Charge trap is a core principle for storing information in memory semiconductors. An international research team led by Korean researchers, including those from Samsung Electronics, has identified the quantum chemical origin of charge traps, putting an end to a debate that has persisted for nearly half a century in semiconductor material science.

The international joint research team, including Choi Woon-yi, Senior Researcher at Samsung Electronics Semiconductor Research Center's CSE (Computational Science & Engineering) team, Professor Hawoong Jeong from KAIST Department of Physics, and Professor Richard Dronskowski from RWTH Aachen University in Germany, has elucidated the charge trap mechanism of "amorphous silicon nitride (a-SiN)," widely used as a charge storage layer in flash memory (CTF), at the atomic level. The research results were published in the international journal "Science Advances" on the 25th.

A charge trap is a phenomenon where electrons become trapped and cannot escape within a semiconductor, and its fundamental cause has not been clearly explained, having been utilized empirically until now. The prevailing theory was that charge traps occur due to a single defect known as "silicon with a broken bond (Si-DB)."

The research team has identified that charge traps arise not from defects in specific types of atoms but from the interactions and chemical bond reorganization of various coordination defects (a state where the bonding regularity between atoms is broken). They have proposed a new paradigm that can explain the characteristics of traps and charge stabilization phenomena that the Si-DB model could not account for.

The research team also confirmed that the charge trap mechanism is connected to the "Negative-U" concept proposed by Nobel laureate Philip Anderson in 1975. Negative-U refers to the tendency in amorphous materials for electrons with broken bonds to attract each other and pair up rather than exist alone. The team confirmed that charge traps result from the interactions where various coordination defects exchange electrons, verifying the chemical reality of Negative-U in amorphous materials, which had existed only theoretically, after half a century.

The team also revealed that the silicon-silicon bond network formed within a-SiN in compositions relatively deficient in nitrogen influences the strength and spatial distribution of charge traps. They proposed an interpretation that amorphous materials are not merely in a state of disorder but are complex systems with statistical regularity and interaction structures.

Senior Researcher Choi stated, "This study goes beyond the limitations of the existing Si-DB model, which explained charge traps as a single type of defect, by presenting a new perspective of the interactions of coordination defects. It is significant in that it provides a new framework for interpreting the electronic structure of amorphous materials."

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