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 Al
₂
O
₃
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 Al
₂
O
₃
gate dielectric to the TID response. Radiation-induced-hole trapping is attributed to oxygen vacancies in the Al
₂
O
₃
. The relatively large hysteresis in these devices is attributed primarily to dangling Al bonds in the near-interfacial Al
₂
O
₃
. Analysis of the temperature dependence of V
_th
and SS suggests that the rate at which electrons leave the Al
₂
O
₃
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.