STRUCTURAL AND ELECTRONIC-PROPERTIES OF THE BI/GAP(110) INTERFACE

A systematic investigation of Bi on n-type GaP(110) with scanning tunneling microscopy (STM), scanning tunneling spectroscopy (STS), and ballistic-electron-emission microscopy(BEEM) is presented. The first 3 angstrom of Bi grows in a quasiordered monolayer, forming alternating chain and vacancy segments along the Ga-P zigzag chains with a periodicity of about 23 angstrom, which is consistent with the observed 6 X 1 low-energy electron diffraction (LEED) pattern. Additional Bi atoms aggregate to form congruent-to 10-angstrom-high clusters, which suggests a Stranski-Krastanov growth mode. The STS results show that the Bi monolayer is semiconductorlike with a band gap of about 0.55 eV; in contrast, the clusters exhibit metallic character. A 50-angstrom Bi film exhibited monocrystalline and atomically flat regions congruent-to 1000 angstrom in extent, which are delineated from similar adjacent regions by height differences equal to a biatomic step. LEED shows an ordered, two-domain hexagonal surface structure that consists of a close-packed-hexagonal arrangement of Bi atoms, as observed by STM. BEEM reveals a uniform Schottky-barrier height of 1.11 +/- 0.02 eV at all measured positions across the sample surface.