On the Enhancement of the Drain Current in Indium-Rich InGaAs Surface-Channel MOSFETs

The effects of interface-trap states
$(D_{\rm it})$
and the shift of the charge neutrality level (CNL) on the enhancement of the drain current in In-rich surface-channel enhancement-mode n-type InGaAs MOSFETs are investigated. In addition to the increase in the bulk mobility, the shift of the CNL toward the conduction band together with high densities of
$D_{\rm it}$
is responsible for the experimentally observed remarkable enhancement of the on-state drain current with increasing In content in the channel. However, when
$D_{\rm it}$
is low, current enhancement is weak, and the location of the CNL has little effect on the current enhancement. Acceptor-type interface-trap states above the conduction-band minima (CBM) play an important role in determining the inversion-layer electron mobility. Representing
$D_{\rm it}$
distribution above the CBM by a constant equal to the
$D_{\rm it}$
value at the CNL causes an overestimation of the drain current at higher gate voltages. It is also observed that the extraction of
$D_{\rm it}$
from the low-frequency gate
$C$
–
$V$
data is independent of the location of the CNL. We further show that the subthreshold slope (SS) is doubled due to
$D_{\rm it}$
. However, the location of the CNL or the magnitude of
$D_{\rm it}$
above the CBM has little effect on the SS.