Observation of carrier concentration dependent spintronic terahertz emission from n-GaN/NiFe heterostructures

The development of terahertz (THz) spintronics has created a paradigm shift in the generation of THz radiation through the combination of ultrafast magnetism and spin-based electronics. However, research in this area has primarily focused on all-metallic devices comprising a ferromagnetic thin film adjacent to a non-magnetic heavy metal. Here, we report the experimental observation of spintronic THz emission from an n-doped wide bandgap semiconductor, n-GaN. We found that the amplitude of THz emission strongly depends on the carrier concentration of the semiconductor layer, which could be attributed to the tunable Rashba state occurring at the n-GaN/ferromagnet interface. Our work offers exciting prospects for pursuing wide bandgap semiconductor-based spintronic THz devices and demonstrating their intriguing spin Hall physics at the ultrafast timescale.