Structural and electronic properties of the Bi/GaP(110) interface

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Abstract
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 Å 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 Å, which is consistent with the observed 6×1 low-energy electron diffraction (LEED) pattern. Additional Bi atoms aggregate to form ≃10-Å-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-Å Bi film exhibited monocrystalline and atomically flat regions ≃1000 Å 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.