Carrier-removal rate and mobility degradation in heterojunction field-effect transistor structures

In this paper, we report experimental results and theoretical investigations of neutron irradiation-induced carrier-removal rate and mobility degradation in AlGaAs/GaAs heterojunction field-effect transistor structures. The measured two-dimensional (2-D) carrier removal rate of /spl sim/6.0 /spl times/ 10/sup -3/ is found to be consistent with a net (volume) introduction rate of /spl sim/20 cm/sup -1/ acceptor-like defects in the GaAs layer. Radiation-induced acceptors in the GaAs layer have the most significant effect on the 2-D electron concentration, whereas the acceptors in AlGaAs layer have negligible effect for neutron fluence up to 5 /spl times/ 10/sup 14/ cm/sup -2/. The measured 77-K mobility degradation, which is very sensitive to ionized impurity scattering, however, suggests that the introduction rate of the combined donor-like and acceptor-like defects is almost an order of magnitude higher (200 cm/sup -1/). The 300-K mobility, which is dominated by polar-optic phonon scattering, shows only marginal degradation.