Miyazawaetal. [Appl. Phys. Lett.43, 853 (1983)] have recently established a spatial correlation between variations in field‐effect transistor performance and nonuniformities in the cathodoluminescence (CL) efficiency of semi‐insulating (SI) GaAs substrates. In this study, we compare the CL uniformity of both Cr‐doped and undoped SI GaAs crystals grown by the liquid‐encapsulated Czochralski (LEC) technique with undoped SI crystals grown by the horizontal gradient freeze (HGF) technique. In contrast to the LEC crystals, HGF GaAs has extremely uniform CL characteristics which should result in uniform device performance.