Field-Effect Mobility of InAs Surface Channel nMOSFET With Low Scaled Gate-Stack

Frequency (100 Hz ≤ f ≤ 1 MHz) and temperature (-50 ≤ T 20 °C) characteristics of low interface state density D_it high-κ gate-stacks on n-InAs have been investigated. Capacitance-voltage (C-V) curves exhibit typical accumulation/depletion/inversion behavior with midgap D_it of 2 × 10¹¹ and 4 × 10¹¹ cm^-2 eV^-1 at -50 °C and 20 °C, respectively. Asymmetry of low-frequency C-V curves and C-T dependence for negative voltage showing a sharp transition of ≅-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 μm, channel thickness = 10 nm, and equivalent oxide thickness (EOT) 1 ≤ EOT ≤ 1.6 nm have been fabricated. For EOT = 1 nm, a subthreshold swing S = 65 mV/decade, transconductance g_m = 1.6 mS/μm, and ON-current I_ON = 426 μA/μm at an OFF-current I_OFF = 100 nA/μm (supply voltage V_dd = 0.5 V) have been measured. Peak electron field-effect mobilities of 6000-7000 cm²/Vs at sheet electron densities of 2-3 × 10¹² cm^-2 were obtained for EOT as small as 1 nm.