| Despite a historical legacy of rigorous investigation, the origin of metal-semiconductor diode non-idealities remains partly conjecture. Rectifying metal-semiconductor diodes made with the best available technology have been observed to exhibit behavior only partly accounted for by conventional theories. Such behavior includes curved Richardson plots, ideality factors not equal to 1, and excess low frequency noise. In spite of the efforts of theorists to account for these observed non-idealities within the framework of a single barrier height at the metal-semiconductor interface, non-ideal behavior can only be partially explained.;This work examines the electronic properties of metal-semiconductor interfaces using a Scanning Tunneling Microscope (STM)-based technique known as Ballistic Electron Emission Microscopy (BEEM). Direct observation of hot carrier transport across diode energy barriers can be made by this technique. Such observations are localized to the area of the interface immediately underneath the STM tip, which gives BEEM a spatial resolution unique among techniques which probe the electronic structure of these interfaces. In this work, BEEM has been used to evaluate electron transport and barrier height non-uniformities in Au/Si, Au/GaAs, Au/PtSi/Si, Au/InxGa1-x P , Au/ZnSe, Au/GaN and Pt/GaN. This is combined with conventional current vs. voltage and capacitance vs. voltage measurements for comparison. Transmission Electron Microscopy is used for structural characterization and interpretation of the BEEM-derived data for Au/GaAs, Au/PtSi/Si Au/ZnSe, and Au/GaN. Interface properties contributing to spatial inhomogeneities are modeled and interpreted with respect to their contribution to BEEM measurements. BEEM is shown to be an effective probe of interface properties, allowing determination of fundamental interface and transport properties of hot electrons. |
