Effect of Gate Voltage Stress on InGaAs MOSFET With HfO2or Al2O3Dielectric

Abstract

InGaAs nMOSFETs with Al2O3 and HfO2 as dielectric are analyzed. The devices with Al 2O3 show a slightly better subthreshold slope. Both high- $\kappa$ 's have an equal transconductance frequency dispersion $(g_{m}\mbox{-}f)$ . A reduction of $g_{m}\mbox{-}f$ is reached by scaling the HfO2 thickness. Positive gate stress leads to an increase in threshold voltage and subthreshold slope for all oxides. DC- $g_{\max}$ degradation is related purely to creation or activation of additional border traps during stress. The RF- $g_{\max}$ is not degraded. Similar time constants hint to a relation between the (semi-)stable degradation of DC- $g_{\max}$ and the threshold voltage increase. For the samples with HfO2, the effects of gate-stress induced additional border traps can only be detected at low frequencies. The created or activated defects are most likely located deep in the oxide. For Al2O3, the effect of additional border traps is also measurable at higher frequencies. The defects are created both closer to the Al2O3/InGaAs interface and deeper in the oxide.