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

研究了GaAs/GaAlAs异质界面上二维电子气体的场发射特性。研究的目的是阐明二维电子气体通过垂直于异质界面的表面势垒的隧穿现象。在GaAs堆积层中的二维电子气具有高迁移率和相干性。测量发射电子的能量分布和时间响应以及观察场发射模式是本实验研究的目标。在具有超晶格结构的砷化镓晶圆角处制备原子清洁顶点结构是研究项目中的一项重要实验技术。我们开发了一种与超高真空环境相适应的解理机制。GaAs晶圆在（100）平面上沿<011>和<011>方向的解理形成尖角为90度的锋利边缘。顶点曲率半径小于10nm，足够小，可以在表面保持较高的场强。我们从顶点观察到一个平面发射模式。为了测量皮秒脉冲激光光激发后的能量分布和时间响应，我们还开发了能量分辨率为20 meV的半球形静电分析仪和时间分辨率为50ps的单电子检测高灵敏度的条纹相机系统。利用这些新开发的装置，我们将测量发射电子的能量分布和时间响应。

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.