Total-Ionizing-Dose Effects in InGaAs MOSFETs With High-k Gate Dielectrics and InP Substrates

The total-ionizing-dose (TID) response of indium gallium arsenide (InGaAs) MOSFETs with Al2O3 gate dielectrics and several channel lengths is evaluated under different biases. DC static characteristics show large negative threshold voltage Vth shifts and subthreshold stretchout (SS), indicating net positive charge trapping in the gate oxide and generation of the interface and border traps. Hysteresis and Id - Vgs measurements from cryogenic to high temperatures show the important role of defects in the Al2O3 gate dielectric to the TID response. Radiation-induced-hole trapping is attributed to oxygen vacancies in the Al2O3. The relatively large hysteresis in these devices is attributed primarily to dangling Al bonds in the near-interfacial Al2O3. Analysis of the temperature dependence of Vth and SS suggests that the rate at which electrons leave the Al2O3 during a positive-to-negative gate-bias sweep is higher than the rate at which they enter during a negative-to-positive gate-bias sweep.