Charge Collection Mechanisms in AlGaN/GaN MOS High Electron Mobility Transistors

Charge collection mechanisms in AlGaN/GaN MOS-HEMTs are investigated. Device types include those with no gate oxide, and those with HfO₂ and Al₂O₃ gate oxides. Simultaneous charge collection is observed at the gate and the drain or the source, depending on strike location. Heavy ion data coupled with device simulations show that the introduction of a thin HfO₂ layer in the gate stack introduces only a small valence band barrier, reducing but not preventing collection of holes at the gate in HfO₂-gate devices. Furthermore, using Al₂O₃ gate oxide increases the valence band barrier over that of the HfO₂, to the point where the radiation-induced transient is not detectable.