  We fabricated spin-polarized surface electronic states with tunable Fermi
level from semiconductor to low-dimensional metal in the
Bi/GaSb(110)-(2$\times$1) surface using angle-resolved photoelectron
spectroscopy (ARPES) and spin-resolved ARPES. The spin-polarized surface band
of Bi/GaSb(110) exhibits quasi-one-dimensional character with the Rashba
parameter $\alpha _{\rm R}$ of 4.1 and 2.6 eV\AA \ at the $\bar{\Gamma}$ and
$\bar{\rm Y}$ points of the surface Brillouin zone, respectively. The Fermi
level of the surface electronic state is tuned in situ by element-selective
Ar-ion sputtering on the GaSb substrate. The giant Rashba-type spin splitting
with switchable metallic/semiconducting character on semiconductor substrate
makes this system a promising candidate for future researches in
low-dimensional spintronic phenomena.
