Indium phosphide substrate, method of inspecting indium phosphide substrate, and method of producing indium phosphide substrate

An indium phosphide substrate having a first main surface and a second main surface,

• the first main surface having a surface roughness Ra1 at a center position and surface roughnesses Ra2, Ra3, Ra4, and Ra5 at four positions, the four positions being arranged equidistantly along an outer edge of the first main surface and located at a distance of 5 mm inwardly from the outer edge,
• an average value m1 of the surface roughnesses Ra1, Ra2, Ra3, Ra4, and Ra5 being 0.4 nm or less,
• a standard deviation σ1 of the surface roughnesses Ra1, Ra2, Ra3, Ra4, and Ra5 being 10% or less of the average value m1,
• the second main surface having a surface roughness Ra6 at a center position and surface roughnesses Ra7, Ra8, Ra9, and Ra10 at four positions, the four positions being arranged equidistantly along an outer edge of the second main surface and located at a distance of 5 mm inwardly from the outer edge,
• an average value m2 of the surface roughnesses Ra6, Ra7, Ra8, Ra9, and Ra10 being 0.2 am or more and 3 am or less, and
• a standard deviation σ2 of the surface roughnesses Ra6, Ra7, Ra8, Ra9, and Ra10 being 10% or less of the average value m2.