Abstract: Total liquid encapsulated vertical gradient freeze (VGF) method has been used to grow undoped semi-insulating (SI) GaAs crystals. The impurities such as silicon and carbon have been well controlled in the growth process. As a result, a 2" diameter undoped SI GaAs single crystal was achieved. Materials characterization tests demonstrated the Hall parameters of the crystal close to that of LEC crystal, and dislocation densities of 8600 cm^-2, about one order of magnitude lower than dislocation densities of LEC crystals.