Light‐Induced Colossal Magnetoresistance and Ultrasensitive Hall Resistance of Intrinsic Silicon

Abstract Due to their unique energy level structure and high kinetic energy, photoexcited hot carriers exhibit excellent performance from thermally excited carriers in semiconductors. Here, the electrical transport properties of photoexcited hot carriers in intrinsic monocrystalline silicon at 10 Kelvin, where traditional thermally excited carriers can be neglected are reported. Compared to thermally excited carriers, hot carriers exhibit several notable differences: an increase in carrier mobility of ≈2–3 orders of magnitude, up to ≈10⁶ cm² Vs⁻¹; an increase in magnetoresistance of ≈5 orders of magnitude, up to ≈6.4 × 10⁴ % at 1 Tesla, which is more prominent than almost all topological materials under the same conditions, and a novel hot‐carrier‐dependent Hall effect with ultrahigh linear Hall field sensitivity (≈ 3.2 × 10⁷ Ω T⁻¹) is observed. The large measured magnetoresistance is replicated by Floquet–Keldysh quantum transport simulations of the light‐irradiated two‐terminal gapped device, provided that it includes spin‐orbit coupling (SOC). While SOC effects are minor in intrinsic Si, it is interpreted as additional ones arising due to inversion symmetry breaking in the effective heterostructure photoexcited‐Si/plain‐Si. These findings exemplify a new paradigm of light‐induced phenomena in a mundane solid‐state material, opening new avenues for light‐driven, low‐power consumed, and ultrahigh field sensitivity hot carrier devices.