Electrostatic discharge effects on AlGaN/GaN high electron mobility transistors on sapphire substrates

The effects of electrostatic discharge (ESD) on the variation of electrical characteristics of AlGaN/GaN high electron mobility transistors (HEMTs), such as on-current, leakage current of gate and transconductance (g(m)), have been investigated. The failure phenomena of HEMTs due to the ESD stress have also been studied. We have applied the ESD stress by transmission line pulsing (TLP) method, which is widely used in ESD stress experiments, and measured the electrical characteristics before and after applying ESD stress. The on-current after applying ESD stress was increased because the space between the drain and the gate was narrowed due to the migration of the metal caused by the high electric field and temperature under the ESD stress. The leakage current was decreased and g(m) was changed slightly. The failure points were located mainly in the middle and on each side of the gate. AlGaN/GaN HEMTs, in contrast with GaAs HEMTs, have been shown to easily fail due to the poor thermal characteristics of the sapphire substrate.