Direct Mapping of Crystallization-Induced Trap-State Modulation and Its Impact on Local Carrier Mobilities in Indium Oxide Thin-Film Transistors

Abstract

Crystalline oxide semiconductors are promising back-end-of-line (BEOL)-compatible channel materials for AI hardware, yet their nanoscale trap physics remains unclear. Here, we directly mapped and quantified mobility (mu), trap density (N eff), and trap depth in amorphous/nanocrystalline (a/n-) and polycrystalline (p-) In2O3 films using scanning noise microscopy with finite-element analysis. A/n-In2O3 exhibited large local variations in mu and N eff with deep trap states (similar to 0.24 eV). Upon full crystallization, p-In2O3 exhibited uniform mu and N eff with shallow trap states at grains (similar to 0.10 eV) and grain boundaries (similar to 0.12 eV). Crystallization effectively eliminated structural-disorder-induced deep states, leaving only shallow donor-like oxygen vacancy traps. This led to enhanced mu and significantly reduced N eff (and trap depth), exhibiting uniform spatial distributions with minute changes at grain boundaries. Furthermore, p-In2O3 devices achieved higher mobility, more positive threshold voltage, and improved bias stability, confirming reduced deep-trap activity and enhanced charge-transport uniformity. This work establishes a direct link between structural ordering, local trap-depth modulation, and macroscopic electrical performances of crystalline oxide channels.