Efectos térmicos y trampa en los transistores AlGaN/GaN HEMT

Abstract

Traps effects (due to the presence of surface-state densities and deep-levels) in AlGaN/GaN HEMT devices cause slow current transients referred as gate-lag and drain-lag effects that become a cause of so called current collapse. Current collapse is a reversible reduction of drain-current when both the gate and drain voltages are changed abruptly. This effect cause important deviation between DC and dynamic I/V characteristics that limits the output power of the device at high frequencies. In addition, traps state depends on thermal and illumination conditions of the device. Energy from the illumination and temperature supports the electrons captured in traps states to overcome the energy-barrier to the conduction band. In order to improve the device performance and reliability, understanding the current collapse effects is critical, and it must be taken into account when an accurate large-signal dynamic model is needed. In this paper, drain-current collapse due to gate-lag and drain-lag effects as well as the effects of temperature on traps state are characterised based on pulsed measurements technique.