  We report our demonstration of Rabi oscillations in Si-SiO2-Al
photoconductive devices with nanosecond laser pulses of a few nJ at room
temperature without external magnetic fields. Zeeman splitting of spin quantum
states of dopants in silicon is achieved with internal magnetic fields produced
by the Al film under excitation of laser pulses. Rabi oscillation frequency is
15 MHz and 25 MHz when photocurrent direction is perpendicular and parallel,
respectively, to the propagation direction of linearly-polarized, 532-nm, 7-ns
laser pulses. Insertion of graphene buffer layer between Al and SiO2 provides a
three-fold enhancement in Rabi oscillation amplitude. This simple-structured,
low-cost device operated at room temperature should open a new avenue for
future spin-based electronics and optoelectronics.
