High energy neutron irradiation effects in GaAs modulation-doped field effect transistors (MOSFETs): threshold voltage

The effects of high energy neutrons on MODFETs were studied for fluences approaching 1×10¹⁵ cm^-2. Neutron-induced threshold-voltage shifts are described by application of a finite-temperature, strong-inversion, depletion-layer, charge-control model. The model indicates that the shifts are a consequence of electron trapping in 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 acceptor introduction rate, and applying the charge-control model to relate this introduction rate to the threshold voltage. The analysis shows that neutron degradation in these heterostructures is dominated by the change in the depletion layer charge and the shift in the Fermi level with neutron fluence. These dominant mechanisms depend on GaAs material parameters only