Field Emission from two dimensional electrons at a hetero-interface of superlattice and application to picosecond pulse electron source

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Field emission property of two dimensional electron gas at a GaAs/GaAlAs heterointerface was studied. The aim of the research is to elucidate the tunneling phenomena of two-dimensional electron gas through a surface potential barrier perpendicular to the heterointerface. The two-dimensional electron gas localized in a accumulation layer of GaAs is featured by its high mobility and coherence. The measurement of energy distribution and time response of emitted electrons together with the observation of field emission pattern is a target of this experimental study.Fabrication of atomically-clean apex structure at a corner of the GaAs wafer with superlattice structures was an important experimental technique in the research program. We have developed a cleavage mechanism compatible with ultrahigh vacuum environment. Cleavage along <011> and <011> direction on a (100) plane of a GaAs wafer makes a sharp edge with an apex angle of90o. The curvature radius of the apex was less than 10nm, which is small enough to keep high field strength at the surface. We have observed a planer emission pattern from the apex. For the measurement of energy distribution and time response after photo excitation by a picosecond pulse laser, we have also developed a hemispherical electrostatic analyzer with energy resolution of 20 meV and a streak-camera system which has high sensitivity for single electron detection with time resolution of 50ps. By utilizing these newly developed devices, we are going to measure the energy distribution and the time response of the emitted electrons.