Field-Effect Mobility of InAs Surface Channel nMOSFET With Low $D_{\rm it}$ Scaled Gate-Stack

Frequency (100 ${\rm Hz}\le f \le 1$ MHz) and temperature ( $- 50 \le T \le 20^{\circ }\text{C}$ ) characteristics of low interface state density $D_{\rm {it}}$ high- $\kappa $ gate-stacks on n-InAs have been investigated. Capacitance–voltage ( $C$ – $V$ ) curves exhibit typical accumulation/depletion/inversion behavior with midgap $D_{\rm {it}}$ of $2\times 10^{11}$ and $4\times 10^{11}$ cm $^{-2}$ eV $^{-1}$ at −50 °C and 20 °C, respectively. Asymmetry of low-frequency s $C$ – $V$ curves and $C$ – $T$ dependence for negative voltage showing a sharp transition of $\cong -20$ dB/decade between low- and high-frequency behavior indicate surface inversion. An inversion carrier activation energy and an InAs hole lifetime of 0.32 eV and 2 ns have been extracted, respectively. Surface channel nMOSFETs with gate length $L_{g} =$ 1 $\mu \text{m}$ , channel thickness = 10 nm, and equivalent oxide thickness (EOT) $1 \le {\rm EOT} \le 1.6$ nm have been fabricated. For ${\rm EOT} = 1$ nm, a subthreshold swing $S = 65$ mV/decade, transconductance $g_{m} =1.6$ mS/ $\mu \text{m}$ , and ON-current $I_{{\mathrm{{\scriptscriptstyle ON}}}} =$ 426 $\mu \text{A}/\mu \text{m}$ at an OFF-current $I_{{\mathrm{{\scriptscriptstyle OFF}}}} =100$ nA/ $\mu \text{m}$ (supply voltage $V_{\rm {dd}} =$ 0.5 V) have been measured. Peak electron field-effect mobilities of 6000–7000 cm $^{2}$ /Vs at sheet electron densities of 2– $3\times 10^{12}$ cm $^{-2}$ were obtained for EOT as small as 1 nm.