Crystal and substrate of conductive GaAs, and method for forming the same
An electrically conductive GaAs crystal has an atomic concentration of Si more than 1×10 17 cm −3 , wherein density of precipitates having sizes of at least 30 nm contained in the crystal is at most 400 cm −2 . In this case, it is preferable that the conductive GaAs crystal has a dislocation density of at most 2×10 −2 cm 2 or at least 1×10 −3 cm 2 .
1. A method for producing a conductive GaAs bulk crystal, the conductive GaAs bulk crystal having an atomic concentration of Si more than 1×10 17 cm −3 , and a density of precipitates having sizes of at least 30 nm contained in the crystal being at most 400 cm −2 , the method comprising:
growing the conductive GaAs bulk crystal in a growth furnace; and
after the whole quantity of GaAs melt is crystalized, maintaining a temperature in the growth furnace more than 600° C., and annealing the conductive GaAs bulk crystal at a temperature of at least 1130° C. for at least 10 hours.
2. The method for producing the conductive GaAs bulk crystal according to claim 1 , wherein the conductive GaAs bulk crystal is annealed at a temperature of at least 1160° C.
3. The method for producing the conductive GaAs bulk crystal according to claim 1 , wherein the conductive GaAs bulk crystal is annealed at a temperature of at least 1200° C.