GROUP III-V COMPOUND SEMICONDUCTOR SINGLE CRYSTAL SUBSTRATE AND PRODUCTION METHOD THEREFOR

The group III-V compound semiconductor single crystal substrate has a circular main surface, wherein the main surface has an orientation flat or a notch and has a first region that is inside a first virtual line passing through a point 5 mm away inward from an outer periphery thereof, and a first reference line that is a virtual line segment extending from a center of the main surface to the first virtual line in a direction going from the center of the main surface toward the orientation flat or the notch; on the main surface, the number of particles having a particle size of 0.079 µm or more at each of measurement points at nine points in total is measured, where the nine points are one point at the center, four midpoints of four virtual line segments having angles of 0 degrees, 90 degrees, 180 degrees, and 270 degrees, respectively, with respect to the first reference line and extending from the center to the first virtual line, and four endpoints of four virtual line segments having angles of 45 degrees, 135 degrees, 225 degrees, and 315 degrees, respectively, with respect to the first reference line and extending from the center to the first virtual line, and a standard deviation and an average value of the number of the particles calculated based on the measurement satisfy a relationship of standard deviation/average value ≤ 0.9.