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 withHfO₂andAl₂ O₃gate 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 thinHfO₂layer in the gate stack introduces only a small valence band barrier, reducing but not preventing collection of holes at the gate inHfO₂-gate devices. Furthermore, usingAl₂ O₃gate oxide increases the valence band barrier over that of theHfO₂, to the point where the radiation-induced transient is not detectable.