The structure and materials of the new high-pressure SBD are different from those of the traditional SBD. The conventional SBD is formed by contacting a metal with a semiconductor. The metal material can be aluminum, gold, molybdenum, nickel and titanium, and the semiconductor is usually silicon (SI) or gallium arsenide (GaAs). N-type semiconductor material is selected as the substrate in order to obtain good frequency characteristics due to high electron mobility than hole mobility. In order to reduce the junction capacitance of SBD and improve the reverse breakdown voltage without making the series resistance too large, a high resistance n-thin layer is usually epitaxed on the N + substrate. Its structure diagram, graphic symbols and equivalent circuit. CP is the shell parallel 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 (both are functions of bias current and bias voltage). As we all know, there are a large number of conductive electrons inside a metal conductor. When the metal is in contact with the semiconductor (the distance between the two is only an order of magnitude of the atomic size), the Fermi level of the metal is lower than that of the semiconductor. The electron density in the metal is smaller than that in the semiconductor conduction band at the energy level corresponding to the semiconductor conduction band. Therefore, after the two contact, electrons will diffuse from the semiconductor to the metal, so that the metal is negatively charged and the semiconductor is positively charged. Since metal is an ideal conductor, the negative charge is only distributed in a thin layer of atomic size on the surface. For n-type semiconductors, the donor impurity atoms that lose electrons become positive ions and are distributed in a large thickness. As a result of the diffusion movement 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 (all the potential barrier regions fall on the semiconductor side). The self built electric field in the barrier region is directed from the n-type region to the metal. With the increase of the self built field of hot electron emission, the drift current opposite to the diffusion current increases, and finally reaches dynamic equilibrium, forming a contact barrier between the metal and the semiconductor, which is the Schottky barrier.
When the applied voltage is zero, the diffusion current of electrons is equal to the reverse drift current, and the dynamic balance is achieved. When a positive bias voltage is applied (i.e., a positive voltage is applied to the metal and a negative voltage is applied to the semiconductor), the self built field is weakened, and the potential barrier on the semiconductor side is lowered, thus forming a positive current from the metal to the semiconductor. When the reverse bias is applied, the self built field is enhanced, the barrier height is increased, and a small reverse current from the semiconductor to the metal is formed. Therefore, SBD, like PN junction diode, is a nonlinear device with unidirectional conductivity.
