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

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 \AA{} 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 \AA{}, which is consistent with the observed 6\ifmmode\times\else\texttimes\fi{}1 low-energy electron diffraction (LEED) pattern. Additional Bi atoms aggregate to form \ensuremath{\simeq}10-\AA{}-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-\AA{} Bi film exhibited monocrystalline and atomically flat regions \ensuremath{\simeq}1000 \AA{} 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\ifmmode\pm\else\textpm\fi{}0.02 eV at all measured positions across the sample surface.