Keita Katayama

We present a thermal simulation study of the KrF excimer laser doping of Sn into β-Ga ₂ O ₃ (010) from a SnO ₂ top layer. Under various conditions, the laser doping experiments and technology computer-aided design (TCAD) simulations were executed, and their results were comparatively analyzed. The transient temperature-field analysis revealed that each laser pulse induced an intense but transient (~ 100 ns) temperature peak confined to a shallow surface region (sub-μm). At a high repetition frequency of 1000 Hz, the incomplete cooling between pulses causes significant heat accumulation at the surface, resulting in enhanced Sn diffusion at 0.3 J/cm ² , whereas it was negligible at 100 Hz. The diffusion lengths were estimated from the simulated temperature results, and they showed good agreement with the Sn depth profiles. These results demonstrate that TCAD-based thermal simulation is effective for describing the temperature field and the dopant diffusion in excimer laser doping of β-Ga ₂ O ₃ .

Magnetic Heusler alloys are highly attractive for spintronics; however, realizing their full potential requires high-temperature annealing, which is often incompatible with practical device fabrication. Excimer laser annealing (ELA) potentially addresses this temperature constraint by making use of the short annealing time and temperature gradient along the depth direction. We investigated the effect of ELA on Co2Mn0.5Fe0.5Ge half-metallic Heusler-alloy thin films and demonstrated that ELA successfully induces crystallization and B2 atomic ordering. Optimized ELA condition using low fluence with a high number of laser irradiations achieved reduced resistivity and negative anisotropic magnetoresistance, indicating improved atomic ordering and high spin polarization, while maintaining flatness of the films. These findings establish ELA as a viable annealing method for integrating high-performance Heusler alloys into the device structure with strict thermal budget. Moreover, ELA offers additional advantages such as enhanced throughput and selective area annealing, thereby broadening the scope of Heusler-alloy applications in spintronic devices.