SBH

Schottky barrier height is the energy difference between the conduction band of a semiconductor and the Fermi level of a metal at their contact interface. When a metal is deposited directly onto a semiconductor, the electrons at the boundary face an energy barrier that controls whether current flows easily or gets blocked. That barrier height, measured in electron volts, is the SBH. It is a physical quantity, not a design choice: it emerges from the specific pair of materials involved and their atomic structure at the junction.

SBH matters most in Schottky diodes and metal-semiconductor field-effect transistors (MESFETs), where the barrier controls the forward voltage drop and reverse leakage current. A lower SBH means easier forward conduction but typically higher reverse leakage; a higher SBH does the opposite. In silicon devices, SBH values typically range from 0.5 to 0.9 electron volts depending on the metal. Gallium arsenide and silicon carbide show different values entirely, and choosing the metal contact is partly a question of achieving the SBH needed for the application.

Why SBH varies and how to measure it

The barrier height is not determined by the work functions of the two materials alone, as simple theory might suggest. Interface chemistry, surface states, and defects all play a role. Metal deposition conditions, temperature, and even contamination can shift the effective SBH by tenths of an electron volt. This variability is a real problem in manufacturing: two wafers processed the same way can show different barrier heights, leading to performance spread in the finished devices.

SBH is measured by techniques such as current-voltage analysis at different temperatures, capacitance-voltage profiling, or photoelectric spectroscopy. The temperature dependence of forward current gives a direct estimate; as temperature changes, the current changes in a way that reveals the barrier height. In production, SBH is a key parameter to monitor because it directly affects yield and circuit performance, especially in high-speed RF applications where leakage current noise becomes significant.

In modern wide-bandgap semiconductors like silicon carbide and gallium nitride, SBH control is critical because the larger bandgaps make it harder to achieve low barriers naturally. Researchers and device engineers spend considerable effort tuning contact metals and surface treatments to shift SBH into the desired range. Understanding and controlling SBH remains one of the persistent challenges in scaling power electronics and RF devices to higher frequencies and voltages.