Gallium arsenide single crystal substrate and method of producing same
A gallium arsenide single crystal substrate is a gallium arsenide single crystal substrate having a main surface having a circular shape, wherein an average value of a dislocation density of the main surface is 5 cm −2 or more and 100 cm −2 or less, and in an imaginary grid formed by laying out squares each having each side of 2 mm on the main surface such that a largest number of the squares are arranged side by side without overlapping with each other, a ratio of the number of squares in which no dislocation is present to a total number of the squares constituting the grid is 97.0% or more and 99.5% or less, the gallium arsenide single crystal substrate including silicon, wherein a concentration of the silicon is 1.0×10 18 cm −3 or more and 5.0×10 19 cm −3 or less.
1 . A gallium arsenide single crystal substrate comprising a main surface having a circular shape, wherein
an average value of a dislocation density of the main surface is 5 cm −2 or more and 100 cm −2 or less,
in an imaginary grid formed by laying out squares each having each side of 2 mm on the main surface such that a largest number of the squares are arranged side by side without overlapping with each other, a ratio of the number of squares in each of which no dislocation is present to a total number of the squares constituting the grid is 97.0% or more and 99.5% or less, and
a diameter of the gallium arsenide single crystal substrate is 70 mm or more,
the gallium arsenide single crystal substrate comprising silicon, wherein
an atomic concentration of the silicon is 1.0×10 18 cm −3 or more and 5.0×10 −19 cm −3 or less, and
a carrier concentration of the gallium arsenide single crystal substrate is 1.0×10 −18 cm −3 or more and 4.0×10 −18 cm −3 or less.
2 . The gallium arsenide single crystal substrate according to claim 1 , wherein
a crystal plane of the main surface is a {100} plane of a gallium arsenide single crystal or a plane having an off angle of more than 0° and 3° or less with respect to the {100} plane of the gallium arsenide single crystal,
the dislocation is included in a slip line, and
the slip line is present along at least one direction selected from a group consisting of four directions equivalent to a [01-1] direction of the gallium arsenide single crystal, so as to extend from an outer periphery of the main surface toward an inner side of the main surface.
3 . The gallium arsenide single crystal substrate according to claim 1 , wherein the diameter of the gallium arsenide single crystal substrate is 70 mm or more and 210 mm or less.
4 . The gallium arsenide single crystal substrate according to claim 2 , wherein the diameter of the gallium arsenide single crystal substrate is 70 mm or more and 210 mm or less.
5 . The gallium arsenide single crystal substrate according to claim 1 , comprising boron, wherein
an atomic concentration of the boron is 1.0×10 18 cm −3 or more and 1.0×10 19 cm −3 or less.
6 . A method of producing a gallium arsenide single crystal substrate having a main surface having a circular shape, the method comprising:
obtaining a gallium arsenide single crystal by performing crystal growth using a gallium arsenide single crystal growth apparatus; and
obtaining the gallium arsenide single crystal substrate by processing the gallium arsenide single crystal, wherein
the gallium arsenide single crystal growth apparatus includes a crucible, a crucible holding base that holds the crucible, and a heating element that heats the crucible,
the crucible includes a seed crystal accommodation portion having a cylindrical shape, an increased-diameter portion connected to the seed crystal accommodation portion, and a straight barrel portion connected to the increased-diameter portion,
the seed crystal accommodation portion has a hollow portion, the hollow portion being opened on a side on which the seed crystal accommodation portion is connected to the increased-diameter portion, the hollow portion being provided with a bottom wall formed on a side opposite to the increased-diameter portion,
the increased-diameter portion has a truncated conical shape having a diameter that is increased upward in an axial direction of the crucible, and is connected to the seed crystal accommodation portion on a small diameter side of the increased-diameter portion,
the straight barrel portion has a hollow cylindrical shape and is connected to a large diameter side of the increased-diameter portion,
the crucible holding base holds the increased-diameter portion without contact with the straight barrel portion, and
when an inner diameter of the straight barrel portion is represented by D1 and an outer diameter of the crucible holding base is represented by D2, the D1 and the D2 satisfy a relation of 1.05≤D2/D1<1.5, and a unit of each of the D1 and the D2 is mm.
7 . The method of producing the gallium arsenide single crystal substrate according to claim 6 ,
the obtaining the gallium arsenide single crystal includes
accommodating the seed crystal into the seed crystal accommodation portion and accommodating gallium arsenide in a form of a lump together with silicon into each of the increased-diameter portion and the straight barrel portion,
melting a part of the seed crystal and the gallium arsenide into a gallium arsenide melt by heating the crucible using the heating element and bringing the gallium arsenide melt into contact with a remainder of the seed crystal, and
performing crystal growth of the gallium arsenide single crystal from the gallium arsenide melt on the remainder of the seed crystal,
the performing the crystal growth is performed while performing control such that a value obtained by performing second-order differentiation onto a temperature at an interface between the gallium arsenide single crystal and the gallium arsenide melt becomes 0.003° C./mm 2 or more and 0.012° C./mm 2 or less, the second-order differentiation being performed at a position of the interface in an axial direction of the crucible,
a positive direction of the position is a direction from a lower side of the crucible toward an upper side of the crucible along the axial direction, and
a concentration of the silicon in the gallium arsenide single crystal substrate is 1.0×10 18 cm −3 or more and 5.0×10 19 cm −3 or less.