Gallium arsenide single crystal substrate and method for producing gallium arsenide single crystal substrate

A gallium arsenide single crystal substrate having a main surface, wherein

• the gallium arsenide single crystal substrate has a disk shape having a diameter greater than or equal to 75 mm and less than or equal to 300 mm,
• when nine measurement points on the main surface are measured by X-ray photoelectron spectroscopy, in which an X-ray having an energy of 150 eV is used and a take-off angle of a photoelectron is set to 5°, an average value of a ratio of a number of As atoms existing as diarsenic trioxide to a number of As atoms existing as diarsenic pentoxide is greater than or equal to 2, and a standard deviation of the ratios is less than or equal to 1,
• when the diameter is set to D mm, and when two axes that pass through a center of the main surface and are orthogonal to each other on the main surface are set to an X-axis and a Y-axis, coordinates (X, Y) of the X-axis and the Y-axis of the nine measurement points are (0,0), (D/4,0), (0,D/4), (−D/4,0), (0,−D/4), ((D−40)/81/2, (D−40)/81/2), (−(D−40)/81/2, (D−40)/81/2), (−(D−40)/81/2, −(D−40)/81/2), and ((D−40)/81/2, −(D−40)/81/2), and
• an average value of arithmetic average roughness Ra at the nine measurement points is less than or equal to 0.3 nm.