Effect of Electron Irradiation on Carrier Mobilities in Inversion Layers of Insulated Gate Field Effect Transistors

The effect of 1. 5 MeV and 20 keV electrons on the mobility was determined for a number of different types of n- and p-channel insulated gate field effect transistors with thermally grown oxide and deposited nitride passivation. An expression has been derived for the variation of the effective mobility with gate voltage as the result of surface scattering, which is in good agreement with values obtained from the channel conductance at 100 mV source to drain voltage. It is shown that the observed decrease in effective mobility after irradiation may be explained in terms of increased lattice scattering and Coulomb scattering by charged surface traps while the diffuse surface scattering remains unchanged. The channel conductance and transconductance of the devices were also measured in the saturation region.