Abstract
A modified two-temperature zone horizontal Bridgman (M2T-HB) system to grow high quality GaAs crystals is described in detail. GaAs crystals of 2 inch diameter and 30 cm length can be routinely grown by the M2T-HB technique. Keeping the solid/melt interface flat with the specially designed liner construction and viewing window, as well as eliminating the sticking between the quartz boat and GaAs crystals, lineage defects can be eliminated and the dislocation density can be greatly reduced. Moderately Si-doped GaAs crystals have etch pit densities (EPDs) lower than 2000 cm -2 . For moderately Si-doped GaAs crystals, the best result shows that EPDs are lower than 700 cm -2 in the whole ingot. Nearly dislocation free Si-doped GaAs crystals with high carrier concentration of (1-4)×10 18 cm -3 can also be grown by this technique. Zn-doped GaAs crystals with carrier concentration in the range of (1-5)×10 19 cm -3 have EPD lower than 3000 cm -2 . The carrier concentrations of undoped GaAs crystals are in the range of (5-10)×10 15 cm -3 . The result indicated that high purity GaAs crystals with low Si contamination can be grown by M2T-HB technique. © 1990.