[7p-S45-1~14] 3.7 Laser processing

△ [7p-S45-14] Self-assembled periodic nanostructures in semiconductor

〇Yuta Nakanishi¹, Yasuhiko Shimotsuma¹, Masaaki Sakakura², Kiyotaka Miura¹ (1.Kyoto Univ., 2.Next Generation Laser Processing Technology Research Association)

Keywords:nanograting, semiconductor, femtosecond laser

We have successfully observed self-assembled periodic nanostructures inside Si single crystal and GaP crystal, by the femtosecond double pulse irradiation. These experimentally indicate that the self-assembly inside semiconductors triggered by ultrashort pulses irradiation is possibly associated with a direct or an indirect band gap. More recently we have also empirically classified the photoinduced bulk nanogratings into the following three types: (1) structural deficiency, (2) compressed structure, (3) partial crystallization. We have still a big question about what material properties are involved in the bulk nanograting structure formation. To reveal the relationship between the width of the band gap and the nanograting structure, we have employed β-Ga₂O₃ crystals (indirect bandgap Eg ~ 4.8 eV) as a sample for femtosecond laser irradiation. The nanograting structure inside β-Ga₂O₃ crystal was aligned perpendicular to the laser polarization direction. Such phenomenon is similar to the nanograting in SiO₂ glass (Eg ~ 9 eV).In this study, to clarify the role of Sn doping, we also investigate the photoinduced structure in Sn doped β-Ga₂O₃ crystals. Moreover, we simulated the electronic state in various semiconductors by the first principle calculation and tried to elucidate the relation between electronic state and nanograting.