GaAs SINGLE CRYSTAL WAFER AND METHOD OF MANUFACTURING THE SAME
The present invention provides a GaAs single crystal wafer and a method of manufacturing the same, wherein the wafer is characterized in that, when the strain in the radial direction in the GaAs single crystal wafer is expressed as Sr and the strain in the tangential direction on the circumference of the same is expressed as St, the residual stress in a wafer plane of the semi-insulating GaAs wafer denoted by |Sr−St| is smaller than 1.0×10 −5 in the center area of such wafer plane and in that the wafer has such a region in which the value |Sr−St| is not smaller than 1.0×10 −5 in the outer area and has such a region in which the value |Sr−St| is smaller than 1.0×10 −5 in the direction [011] in the outer area of such wafer plane.
1 . A GaAs single crystal wafer characterized
in that, when the strain in the radial direction in said GaAs single crystal wafer is expressed as Sr and the strain in the tangential direction on the circumference of the same is expressed as St,
the absolute value of the residual stress in a wafer plane of said wafer denoted by |Sr−St| is smaller than 1.0×10 −5 in the center area of such wafer plane and
in that said wafer has such a region in which the value |Sr−St| is 1.0×10 −5 or more in the outer area of such wafer plane and has such a region in which the value |Sr−St| is smaller than 1.0×10 −5 in the direction [011] in said outer area of such wafer plane.
2 . The GaAs single crystal wafer according to claim 1 , wherein the dislocation density of said wafer in said wafer plane is 30,000 count/cm 2 or smaller.
3 . The GaAs single crystal wafer according to claim 1 , wherein the diameter of said wafer is 100 mm or more.
4 . The GaAs single crystal wafer according to claim 2 , wherein the diameter of said wafer is 100 mm or more.
5 . The GaAs single crystal wafer according to claim 1 , wherein the universal hardness of said outer area of said wafer plane is higher than that of said center area of said wafer plane and the universal hardness of said outer area of said wafer plane is higher than that in the direction [011] in said outer area of said wafer plane.
6 . The GaAs single crystal wafer according to claim 5 , wherein the universal hardness of any part of said wafer plane is 4000 N/mm 2 (MPa) or more and the universal hardness of said outer area of said wafer plane, except that of in the direction [011], is 4300 N/mm 2 (MPa) or more.
7 . A method of manufacturing a GaAs single crystal, which is defined in claim 1 , that uses a setup comprising
a crucible, which is mounted on a susceptor, being accommodated in a container and a melt of GaAs, which is melted by heat, and
a liquid sealer being contained in said crucible,
wherein said method applies a technique comprising the steps of
keeping a seed crystal kept touching the liquid phase of said melt of GaAs and
moving said seed crystal and said crucible relatively,
wherein the method is characterized in that
the shape of said solid phase on the solid-liquid interface between said solid phase and said liquid phase under the manufacturing said single crystal is made convex toward said liquid phase side,
the degree of convex of such shape
(a ratio of the length T 1 , which is the distance from said interface between said melt and said liquid sealer to the top end of said convex, and the diameter of said single crystal T 2 , namely T 1 /T 2 ) is made to be 0.25 or more,
the crystal growth rate V 1 in the direction of the relative movement on said solid-liquid interface is made to be 4 mm/hr to 7 mm/hr; and
the cooling rate V 2 of said solid phase is made to be 5° C./hr or lower.