【Epitaxy Papers】Tunable electrical and photoelectric properties of ex-situ Ge-doped Ga₂O₃ thin films by annealing

      Researchers from Xi'an University of Posts & Telecommunications have published a dissertation titled " Tunable electrical and photoelectric properties of ex-situ Ge-doped Ga₂O₃ thin films by annealing " in Materials Science and Engineering: B.

Abstract

      Ex-situ Ge-doped Ga₂O₃ thin films with a double-layer sandwich structure were prepared on c-plane sapphire substrates by alternating atomic layer deposition and electron-beam evaporation, followed by rapid thermal annealing (RTA) at 600–900 °C. The effects of annealing temperature on the structural evolution, chemical states, and optoelectronic properties of the films were systematically investigated. The as-deposited Ge-doped film exhibited a dark current of 4.45 × 10⁻⁸ A, approximately four orders of magnitude higher than that of the undoped film. After 600 °C annealing, Ge predominantly forms metallic clusters, establishing a percolating conductive network that boosts conductivity in dark by nearly five orders and yields the highest responsivity (131.01 A/W). Upon annealing at 700 °C or higher, Ge oxidation and volatilization disrupt this network while introducing severe lattice damage, causing a drastic conductivity drop. The 800 °C-annealed device, despite lower responsivity, achieves optimal photo-to-dark current ratio and fastest decay time (0.05 s) due to extremely low dark current. In contrast, the 900 °C device exhibits relatively high responsivity (18.74 A/W) and the highest specific detectivity (1.47 × 10¹³ Jones), benefiting from improved crystallinity and possible contribution of residual Ge. These results suggest that the optoelectronic properties of ex-situ Ge-doped Ga₂O₃ are not governed solely by substitutional doping, but are more likely determined by the thermally driven interplay among Ge-related clustering, partial dopant activation, defect evolution, and Ge redistribution. These findings provide crucial guidance for optimizing Ga₂O₃-based devices via ex-situ doping.

DOI：

https://doi.org/10.1016/j.mseb.2026.119623