High Energy Neutron Irradiation Effects in GaAs Modulation-Doped Field Effect Transistors (MODFETS): Threshold Voltage

摘要

The effects of high energy neutrons of fluences approaching 1 x 10 to the 15th power per sq cm on MODFETs have been studied. Neutron-induced threshold voltage shifts are described by application of a finite temperature strong inversion, depletion layer, charge control model. The results of this model show that the neutron-induced threshold voltage is a consequence of electron trapping the GaAs layer near the AlGaAs/GaAs interface. This allows a convenient parameterization of the neutron degradation by accounting for these trapped electrons as effective acceptors', defining an effective accetor introduction rate, and applying the charge control model to describe the threshold voltage. Our analysis shows that neutron degradation in these AlGaAs/GaAs heterostructures is dominated by the change in the depletion layer charge and the shift in the Fermi level with neutron fluence. The dominant mechanisms are shown to depend on GaAs material parameters, only. The contribution due the AlGaAs layer carrier removal is <3% of the total threshold voltage shift. rh