Reflectivity, Photoelectric Emission, and Work Function of AlSb

The reflectivity and photoelectric emission from $h\ensuremath{\nu}=2 \mathrm{to} 6$ eV, and the work function, have been measured for (110) surfaces of AlSb ($p$ type, ${N}_{A}=2\ifmmode\times\else\texttimes\fi{}{10}^{17}$ ${\mathrm{cm}}^{\ensuremath{-}3}$) cleaved in high vacuum and covered with various amounts of cesium. The yield of the clean surface is similar to that of other measured III-V compounds. The threshold for photoelectric emission is 5.22\ifmmode\pm\else\textpm\fi{}0.02 eV, corresponding to excitation from the top of the valence band. With a band gap ${E}_{g}=1.62$ eV, the electron affinity is 3.6 eV. The work function is 4.86\ifmmode\pm\else\textpm\fi{}0.05 eV and the Fermi level lies 0.36\ifmmode\pm\else\textpm\fi{}0.07 eV above the top of the valence band at the surface. By deposition of cesium, the work function was lowered to 1.37 eV and the resulting yield spectrum shows structure related to that of the reflectivity. The combined results of reflectivity and photoelectric emission are discussed in terms of the band structure of AlSb.