Growth of Infrared GaAs Crystal by Vertical Bridgman Method

The growth of infrared GaAs crystal is studied via the vertical Bridgman method. The pulling down furnace temperature is controlled at 1 260 ℃. GaAs crystal is grown at a rate of 2.5 mm/h under 10 ℃/cm temperature gradient. Some spontaneously nucleated GaAs single crystal particles with 1-3 mm size are found attach on the outside wall of PBN crucible. The grown GaAs crystal is about 50.8 mm in. diameter and about 140 mm in length. A heterogeneous nucleation is formed in the head of the crystal and some polycrystal is taken place in the tail part. The cut GaAs single crystal is about 100 mm in length and the overall crystalline rate is up to 70%. The obtained GaAs single crystal has excellent crystallization quality. The average etching pits density of the head and tail parts of the crystal is 868 cm^-2 and 1 436 cm^-2, respectively. The resistivity of the crystal is tested on the level of 10⁷ Ω·cm. The infrared transmittance of the whole GaAs crystal is about 55% (nearly reaches the highest theory value 55. 8%), which can meet the requirements for industry application.