Static and dynamic transconductance of MOSFETs

A model for the dynamic transconductance of small-channel-length MOSFETs operating in the linear region is presented. The model includes the effects of interface traps and their frequency-dependent admittance, Coulombic scattering due to all charges near the Si-SiO₂ interface, and surface roughness scattering. This model is used to explain the behavior of measured devices that have been subjected to ionizing radiation that introduces charges in the insulator and at the insulator-semiconductor interface. In particular, it is shown that the transconductance peak increases with the frequency of operation. The size of this effect is related mainly to the density of interface traps but is also controlled by the number of trapped charges near the Si-SiO ₂ interface, which increases during irradiation. Static and high-frequency measurements of the transconductance of n-channel MOSFETs are compared with simulated results using the proposed model