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.