The change in sheet resistance of an SF6/CHF3 plasma-exposed AlxGa1-xAs (x = 0.30, 0.15) epilayer before and after annealing was investigated and compared with that for GaAs. The sheet resistance of plasma-exposed AlxGa1-xAs (x = 0.30, 0.15) increases further after 300 degrees C annealing, while that of GaAs remained unchanged. After 450 degrees C annealing, the resistivity of plasma-exposed AlxGa1-xAs(x = 0.30) was still higher, while damage in AlxGa1-xAs (x = 0.15) and GaAs had completely vanished. The increased resistivity in AlxGa1-xAs (x = 0.30, 0.15) after annealing was mainly due to further carrier reduction after annealing was mainly due to further carrier reduction by magnification of the damaged region. The effect of annealing on He plasma-exposed AlGaAs was similar to that for SF6/CHF3-plasma-exposed AlGaAs, which suggests that the increased sheet resistance after annealing is related to incorporated low-mass ions, such as He and H. The 4.2 K photoluminescence measurements revealed a new spectral peak near 1.70 eV after annealing, and the peak intensity for the SF6/CHF3 and He plasma-exposed samples was prominent. These results suggest that in-diffusion of point defects by light ions during the annealing extends the carrier reduction in AlGaAs to greater depth.