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Schottky diode structure
Feb 01, 2018

The structure and materials of the new high-pressure SBD are different from the traditional SBD. Traditional SBDs are made of metal and semiconductor contacts. The metal material is aluminum, gold, molybdenum, nickel and titanium. The semiconductors are usually silicon (Si) or gallium arsenide (GaAs). Since electrons have a higher mobility than holes, an N-type semiconductor material is selected as a substrate in order to obtain good frequency characteristics. In order to reduce the junction capacitance of the SBD and increase the reverse breakdown voltage without overcurrent at series resistance, a high-resistance N-epitaxial layer is usually epitaxially grown on the N + substrate. The structure diagram is shown in Figure 1 (a), the graphical symbols and equivalent circuits are shown in Figure 1 (b) and Figure 1 (c). In Figure 1 (c), CP is the shell and shunt capacitance, LS is the lead inductance, RS is the series resistance including the semiconductor body resistance and the lead resistance, Cj and Rj are the junction capacitance and junction resistance, respectively, Bias function). We all know that a large number of conductive metal inside the conductor. When the metal is in contact with the semiconductor (the distance between the two is only on the order of the atomic size), the Fermi level of the metal is lower than the Fermi level of the semiconductor. In the metallic interior and the semiconductor conduction band corresponding to the sub-level, the electron density is smaller than the semiconductor conduction band electron density. Therefore, after the two are in contact, electrons will diffuse from the semiconductor to the metal, causing the metal to be negatively charged and the semiconductor positively charged. Since metals are ideal conductors, negative charges are distributed only within a thin layer of atomic size. In the case of N-type semiconductors, donor-atom atoms that lose electrons become positive ions and are distributed over a larger thickness. As a result of the diffusion of electrons from the semiconductor to the metal, a space charge region, a self-built electric field and a potential barrier are formed, and the depletion layer is only on the side of the N-type semiconductor (the barrier region all falls on the semiconductor side). The self-built electric field in the barrier region is directed to the metal by the N-type region, increases with the increase of the hot electron emission from the built-in field, increases the drift current in the opposite direction to the diffusion current, and finally reaches the dynamic equilibrium, forming a contact potential between the metal and the semiconductor Base, this is Schottky barrier.


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