INVESTIGATION OF THE PLASMON EXCITATION ON HEAVILY DOPED P-TYPE GAAS(110) SURFACE

We present high-resolution electron energy loss measurements on heavily doped p-type GaAs(110), exploiting a wide range of primary beam energies (E(p)). The spectra are remarkably different from those relative to the n-type samples, presenting very broad features and a large background up to several hundreds of meV. The use of different E(p) demonstrated the presence of an intrinsic "dead layer" at the clean semiconductor surface. We could fit the spectra by means of the three-layer model, obtaining a very good agreement. In particular, from the reproduced broad structure we deduced a large value for the plasmon damping, whose origin is discussed and related to the mobility.