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 V-th shifts and subthreshold stretchout (SS), indicating net positive charge trapping in the gate oxide and generation of the interface and border traps. Hysteresis and I-d-V-gs 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 V-th 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.