We have demonstrated room-temperature negative differential resistance (NDR) with a high peak-to-valley ratio (PVR) on the order of 105 using CaF2/CdF2 double-barrier resonant tunneling diode (DBRTD) structures grown on Si(111) substrates. A CdF2 quantum-well layer was grown by molecular-beam epitaxy (MBE) and CaF2 barrier layers were formed by MBE combined with the partially ionized beam technique on an n+-Si(111) substrate with 0.07° miscut, in order to reduce the pinhole density of CaF2 barrier layers. The dispersion of the peak current density and bias voltage of the NDR implies that the layer thickness fluctuation of each CaF2 barrier and CdF2 quantum-well layer is suppressed below ±1 unit layer of the (111) atomic plane for DBRTDs with an 18 µm diameter electrode. The peak and valley currents agreed reasonably with those obtained by theoretical estimation.
We propose a new systematical method to control Schottky barrier heights of metal/semiconductor interfaces by controlling the density of interface electronic states and the number of charges in the states. The density of interface states is controlled by changing the density of surface electronic states, which is controlled by hydrogenation. We apply an establishing hydrogen termination technique for the hydrogenation using a chemical solution, pH controlled buffered HF or hot water. The density of interface charges is changeable by controlling a metal work ftinction. When the density of interface states is completely hydrogenated, the barrier height is determined simply by the difference between a work function of a metal ç4,, and an electron affinity of a semiconductor . In such an interface with zero density of interface states, an Ohmic contact with a zero barrier height is formed when we select a metal with q5,,, < ,. We have already demonstrated controlling Schottky and Ohmic properties by changing the hydrogenation on silicon carbide (0001) surfaces.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.