Ultrafast Photoelectric Effects in Heterojunctions of La_0.7Sr_0.3MnO₃ and Si

Ultrafast photoelectric effects have been observed in p--n heterojunctions of La_0.7Sr_0.3MnO₃(LSMO)/Si and LSMO/SrTiO_3-/Si for the first time. The rise time was about 1 ns and the full width at half maximum was about 2 ns for the photovoltaic pulse when the heterojunction was irradiated by a laser of ～25 ps pulse duration and 1064 nm wavelength. The photovoltaic sensitivity was as large as 435 mV/mJ for a 1064 nm laser pulse. No such pulse was observed with irradiation from a pulsed 10.6 μm CO₂ laser.