X-Ray characterisation of indium phosphide substrates

The perfection of vertical gradient freeze (VGF) and liquid encapsulated Czochralski (LEC) grown 〈001〉 sulphur-doped InP crystals has been studied by high resolution X-ray diffraction and synchrotron X-ray topography. Of those examined, all VGF crystals except one were dislocation-free, the exception having a uniform dislocation density of about 200 cm−2 resulting from slip. The double axis diffraction maps and double crystal topographs showed most crystals to have a uniform lattice curvature. The largest radii of curvature were from VGF wafers, while the smallest values were for LEC wafers.