Atomic‐Level Smoothness on GaAs via Near‐Infrared Femtosecond Single‐Pulse Laser Ablation

ABSTRACT Gallium arsenide (GaAs) is one of the most important semiconductor materials due to its high electron mobility and direct bandgap. However, its high cost limits widespread adoption in applications such as solar cells, which require large amounts of material. The epitaxial lift‐off process allows thin device layers to be separated from the GaAs substrate, enabling substrate reuse. Nevertheless, the resulting poor surface morphology of the processed substrate hinders its reuse for subsequent epitaxial growth. Here, we propose an ultrashort single‐pulse laser ablation method to polish reused GaAs substrates and improve their surface morphology. Leveraging nonlinear light absorption, single‐pulse ablation produces an atomically smooth GaAs surface (∼1 nm roughness) while limiting material removal to less than 76 nm. Additionally, molecular dynamics simulations using the Velocity‐Verlet algorithm, along with a high‐speed real‐time optical measurement system, are employed to analyze the ablation process within 2000 picoseconds (ps) following single‐pulse laser irradiation. This work extends ultrafast laser ablation applications to semiconductor manufacturing and offers an ultrafast imaging solution for laser polishing processes, enabling rapid and repeatable wafer polishing.