Surface passivation techniques for GaAs power Schottky diodes

In recent years, there has been a growing interest in the use of GaAs as a material for high voltage power Schottky diodes. Such devices have been shown to have much lower reverse recovery charge than Si junction diodes and thus to have many potential applications in high-speed switching circuits. However, most Schottky diodes suffer from reverse leakage currents significantly greater than predicted by simple consideration of the Schottky Barrier Height (SBH)-largely as a result of surface leakage. Such problems can be controlled in silicon devices, for which surface passivation methods utilising field oxide and/or electron irradiation are available. By comparison, surface passivation techniques for GaAs devices are relatively undeveloped, although attempts have been made using sulphur and/or selenium coating solutions for low power devices. In this work, we have applied such techniques to power Schottky diodes with the aim of engineering the metal/semiconductor interface to control the forward and reverse characteristics of the device