The temperature distribution in a rectangular sample as a function of time and position during swept line electron beam (SLEB) annealing has been calculated. Beam penetration effects have been included by using the Monte Carlo method and the temperature distribution has been obtained from Green’s function techniques and the method of images. The effects of various beam parameters on the temperature distribution have been studied. The results are correlated with experimental studies of the electrical activation of Be in GaAs during SLEB annealing. The annealing is shown to be governed by a relation of the form: Activated fraction=(Dwell time)×(3840e−(0.535/kBT)).