ELECTRONIC BAND-STRUCTURE OF MONOLAYER BI ON GAP(110)

The two-dimensional electronic band structure of monolayer Bi on GaP(1 10) has been mapped using angle-resolved UV photoelectron spectroscopy (ARUPS) with synchrotron radiation. Surface photovoltage effects are corrected for by simultaneous second-order core spectroscopy. From val ence-band spectra along the four symmetry directions of the surface Br illouin zone at three photon energies it is possible to distinguish th ree states as surface related. The topmost band is found to be inside the fundamental band gap, at ca 0.75 eV above the bulk valence-band ma ximum. Comparison with other V/III-V(110) systems shows that this syst em is not significantly different, despite the relatively large size o f the Bi atoms with respect to the GaP lattice; in a selective compari son with InP and GaAs it would appear that Bi-substrate anion bonding is a more important factor than strain.