Because the yields of GaAs metal‐semiconductor field‐effect transistor (MESFET) devices are negatively impacted if ranges of threshold voltages (Vth) occur for sets of devices fabricated over the total area of the substrate, it is desirable to pinpoint the physical origin of this problem before a solution may be implemented. The presence of high dislocation densities encountered in wafers produced from liquid‐encapsulated Czochralski‐grown boules of GaAs may be responsible for the phenomenon of wide distributions ofVth, although this view is presently controversial. Accordingly, we have implanted silicon as a dopant into commercially supplied semi‐insulating GaAs wafers, formed arrays of MESFETs, and attempted to correlate the dislocation densities determined by Lang x‐ray topography with the magnitude of the scattering ofVth, including the observation of spikes, across the wafers in the ⟨110⟩ direction. The present results indicate that there is no clear correlation between either the magnitudes or the spatial distributions of the threshold voltages and the presence of high densities of dislocations. An alternative explanation is presented based on the presence of point defects such as interstitial arsenic in the samples.