Abstract
Attempts to model the current through Schottky barrier diodes using the two fundamental mechanisms of thermionic emission and tunnelling are adversely impacted by defects and second order effects. This has led to the publication of countless different models to account for these effects, including some with non-physical parameters. Recently, we have developed silicon carbide Schottky barrier diodes that do not suffer from second order effects, such as excessive leakage, carrier generation and recombination, and non-uniform barrier height. In this paper, we derive the foundational current equations to establish clear links between the fundamental current mechanisms and the governing parameters. Comparing these equations with measured current–voltage characteristics, we show that the fundamental equations for tunnelling and thermionic emission can accurately model 4H silicon carbide Schottky barrier diodes over a large temperature and voltage range. Based on the obtained results, we discuss implications and misconceptions regarding barrier inhomogeneity, barrier height measurement, and reverse-bias temperature dependencies.
Highlights
The problem has been the impact of defects and other second order effects, which add highly-variable components to both the forward and reverse currents
Silicon Schottky barrier diodes with aluminium, copper, silver, and gold anodes have been studied for both current directions[7,8,9]
With an adequate edge termination to eliminate the impact of edge leakage, the metal–silicon carbide (SiC) interface is the ideal structure for experimental verification of the fundamental equations for the two principle current mechanisms
Summary
The fundamental current equations can be derived by counting the number of electrons that arrive at the interface at various energy levels, and determining their contribution to the current. For forward bias (Fig. 1a), we can assume that the quasi-Fermi level is flat throughout the space charge region, and we can neglect tunnelling Under these assumptions, the probability P can be taken as 1 when Ekin−x ≥ EF + qφB − qV and 0 otherwise, where qφB is the energy-barrier height, and V is the applied forward-bias voltage. We can approximate the potential energy as trapezoidal, defined by a constant surface electric field, but truncated by the image force A non-truncated potential (one where the image-force rounding is included) is not suitable for the type of fitting we are using due to the increase in computation it requires
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