  A vertical spin metal-oxide-semiconductor field-effect transistor (spin
MOSFET) is a promising low-power device for the post scaling era. Here, using a
ferromagnetic-semiconductor GaMnAs-based vertical spin MOSFET with a GaAs
channel layer, we demonstrate a large drain-source current IDS modulation by a
gate-source voltage VGS with a modulation ratio up to 130%, which is the
largest value that has ever been reported for vertical spin field-effect
transistors thus far. We find that the electric field effect on indirect
tunneling via defect states in the GaAs channel layer is responsible for the
large IDS modulation. This device shows a tunneling magnetoresistance (TMR)
ratio up to ~7%, which is larger than that of the planar-type spin MOSFETs,
indicating that IDS can be controlled by the magnetization configuration.
Furthermore, we find that the TMR ratio can be modulated by VGS. This result
mainly originates from the electric field modulation of the magnetic anisotropy
of the GaMnAs ferromagnetic electrodes as well as the potential modulation of
the nonmagnetic semiconductor GaAs channel layer. Our findings provide
important progress towards high-performance vertical spin MOSFETs.
