COMPARATIVE MOBILITY DEGRADATION IN MODULATION-DOPED GAAS DEVICES AFTER E-BEAM AND X-RAY-IRRADIATION

We report on measured Hall mobility versus temperature for high-quality modulation-doped AlGaAs/GaAs samples after exposure by electrons and x rays at doses and energies typically used in lithography. We find that bare samples exposed by 50 keV electrons suffered significant mobility degradation over the temperature range of 4.2-300 K (as much as a factor of 30). X-ray-exposed samples did not show any mobility degradation. Two-dimensional electron densities were not dramatically affected by either exposure technique, although e-beam exposed samples did show a slight decrease in carrier density. Our results are consistent with previous reports of mobility degradation in some e-beam evaporators.