An indium phosphide substrate having a fi rst main surface and a second main surface, the fi rst main surface having a surface roughness Ral 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 fi rst main surface and located at a distance of 5 mm inwardly from the outer edge, an average value ml of the surface roughnesses Ral, Ra2, Ra3, Ra4, and Ra₅ being 0.4 nm or less, a standard deviation 6l of the surface roughnesses Ral, Ra2, Ra3, Ra4, and Ra₅ being 10 % or less of the average value ml, the second main surface having a surface roughness Ra₆ at a center position and surface roughnesses Ra 7, Ra8, Ra9, and Ra 10 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, Ra 7, Ra8, Ra9, and Ral0 being more than 0.4 nm and 3 nm or less, and a standard deviation 6 2 of the surface roughnesses Ra6, Ra 7, Ra8, Ra 9, and Ra l0 being 10% or less of the average value m2.

An indium phosphide substrate having a fi rst main surface and a second main surface, the fi rst main surface having a surface roughness Ral 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 fi rst main surface and located at a distance of 5 mm inwardly from the outer edge, an average value ml of the surface roughnesses Ral, Ra2, Ra3, Ra4, and Ra₅ being 0.1 nm or more and 0.3 nm or less, a standard deviation 6l of the surface roughnesses Ral, Ra2, Ra3, Ra4, and Ra₅ being 10% or less of the average value ml, the second main surface having a surface roughness Ra₆ at a center position and surface roughnesses Ra 7, Ra8, Ra9, and Ra 10 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, Ra 7, Ra8, Ra9, and Ra₁₀ being 0.5 nm or more and 2 nm or less, and a standard deviation o 2 of the surface roughnesses Ra6, Ra 7, Ra8, Ra 9, and Ra 10 being % or less of the average value m2.

An indium phosphide substrate having a fi rst main surface and a second main surface, the fi rst main surface having a surface roughness Ral 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 fi rst main surface and located at a distance of 5 mm inwardly from the outer edge, an average value ml of the surface roughnesses Ral, Ra2, Ra3, Ra4, and Ra₅ being 0.4 nm or less, a standard deviation 6l of the surface roughnesses Ral, Ra2, Ra3, Ra4, and Ra₅ being 10 % or less of the average value ml, the second main surface having a surface roughness Ra₆ at a center position and surface roughnesses Ra 7, Ra8, Ra9, and Ra 10 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, Ra 7, Ra8, Ra9, and Ral0 being more than 0.4 nm and 3 nm or less, and a standard deviation 6 2 of the surface roughnesses Ra6, Ra 7, Ra8, Ra 9, and Ra l0 being 10% or less of the average value m2.

An indium phosphide substrate having a fi rst main surface and a second main surface, the fi rst main surface having a surface roughness Ral 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 fi rst main surface and located at a distance of 5 mm inwardly from the outer edge, an average value ml of the surface roughnesses Ral, Ra2, Ra3, Ra4, and Ra₅ being 0.1 nm or more and 0.3 nm or less, a standard deviation 6l of the surface roughnesses Ral, Ra2, Ra3, Ra4, and Ra₅ being 10% or less of the average value ml, the second main surface having a surface roughness Ra₆ at a center position and surface roughnesses Ra 7, Ra8, Ra9, and Ra 10 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, Ra 7, Ra8, Ra9, and Ra₁₀ being 0.5 nm or more and 2 nm or less, and a standard deviation o 2 of the surface roughnesses Ra6, Ra 7, Ra8, Ra 9, and Ra 10 being % or less of the average value m2.

An indium phosphide substrate having a fi rst main surface and a second main surface, the fi rst main surface having a surface roughness Ral 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 fi rst main surface and located at a distance of 5 mm inwardly from the outer edge, an average value ml of the surface roughnesses Ral, Ra2, Ra3, Ra4, and Ra₅ being 0.4 nm or less, a standard deviation 6l of the surface roughnesses Ral, Ra2, Ra3, Ra4, and Ra₅ being 10 % or less of the average value ml, the second main surface having a surface roughness Ra₆ at a center position and surface roughnesses Ra 7, Ra8, Ra9, and Ra 10 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, Ra 7, Ra8, Ra9, and Ral0 being more than 0.4 nm and 3 nm or less, and a standard deviation 6 2 of the surface roughnesses Ra6, Ra 7, Ra8, Ra 9, and Ra l0 being 10% or less of the average value m2.

An indium phosphide substrate having a fi rst main surface and a second main surface, the fi rst main surface having a surface roughness Ral 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 fi rst main surface and located at a distance of 5 mm inwardly from the outer edge, an average value ml of the surface roughnesses Ral, Ra2, Ra3, Ra4, and Ra₅ being 0.1 nm or more and 0.3 nm or less, a standard deviation 6l of the surface roughnesses Ral, Ra2, Ra3, Ra4, and Ra₅ being 10% or less of the average value ml, the second main surface having a surface roughness Ra₆ at a center position and surface roughnesses Ra 7, Ra8, Ra9, and Ra 10 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, Ra 7, Ra8, Ra9, and Ra₁₀ being 0.5 nm or more and 2 nm or less, and a standard deviation o 2 of the surface roughnesses Ra6, Ra 7, Ra8, Ra 9, and Ra 10 being % or less of the average value m2.

An indium phosphide substrate having a fi rst main surface and a second main surface, the fi rst main surface having a surface roughness Ral 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 fi rst main surface and located at a distance of 5 mm inwardly from the outer edge, an average value ml of the surface roughnesses Ral, Ra2, Ra3, Ra4, and Ra₅ being 0.4 nm or less, a standard deviation 6l of the surface roughnesses Ral, Ra2, Ra3, Ra4, and Ra₅ being 10 % or less of the average value ml, the second main surface having a surface roughness Ra₆ at a center position and surface roughnesses Ra 7, Ra8, Ra9, and Ra 10 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, Ra 7, Ra8, Ra9, and Ral0 being more than 0.4 nm and 3 nm or less, and a standard deviation 6 2 of the surface roughnesses Ra6, Ra 7, Ra8, Ra 9, and Ra l0 being 10% or less of the average value m2.

An indium phosphide substrate having a fi rst main surface and a second main surface, the fi rst main surface having a surface roughness Ral 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 fi rst main surface and located at a distance of 5 mm inwardly from the outer edge, an average value ml of the surface roughnesses Ral, Ra2, Ra3, Ra4, and Ra₅ being 0.1 nm or more and 0.3 nm or less, a standard deviation 6l of the surface roughnesses Ral, Ra2, Ra3, Ra4, and Ra₅ being 10% or less of the average value ml, the second main surface having a surface roughness Ra₆ at a center position and surface roughnesses Ra 7, Ra8, Ra9, and Ra 10 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, Ra 7, Ra8, Ra9, and Ra₁₀ being 0.5 nm or more and 2 nm or less, and a standard deviation o 2 of the surface roughnesses Ra6, Ra 7, Ra8, Ra 9, and Ra 10 being % or less of the average value m2.