Hole plasmon excitations on ap-type GaAs(110) surface

High-resolution electron-energy-loss spectroscopy (HREELS) is used to study the hole-plasmon excitations in the valence band of heavily doped p-type GaAs(110) surfaces (${\mathit{n}}_{\mathit{H}}$=2.2×${10}^{19}$ ${\mathrm{cm}}^{\mathrm{-}3}$). A single well-defined surface-hole-plasmon peak at an energy of 75 meV was observed by HREELS at low temperature (-80 K). The observed peak is attributed to a coherent excitation of both the light- and heavy-hole plasmas, and its energy position is higher than that expected for either the light-hole or heavy-hole surface plasmon. We demonstrate that the large peak width of the hole-plasmon excitation, for a heavily doped p-type GaAs surface, is due to the low electronic mobility of holes.