Defect analysis in Czochralski-grown Yb:FAP crystal

Growth-induced defects in Yb:FAP crystals grown by the Czochralski method have been investigated by optical microscopy, chemical etching, scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). Anisotropic etching features have been observed on two FAP crystal planes: (0 0 0 1) and (101¯0). The shape of etch pits on the (0 0 0 1) plane is hexagonal, while the etch pits on the (101¯0) plane have a variety of irregular shapes. It is also found that the density of etch pit varies along the boule. Based on the experimental observations, the formation mechanisms of growth defects are discussed, and methods for reducing the growth-induced defect concentration is proposed.