Growth of Boron-Doped Germanium Single Crystals by the Czochralski Method

In this paper, we present the growth of boron-doped germanium single crystals using the Czochralski method. Boron was introduced into the solid phase prior to the initiation of the growth experiment. Enhanced dissolution of boron in the germanium melt was observed at higher temperatures, facilitating the single crystalline growth. The distribution of boron along the crystal length was quantified at several positions using secondary ion mass spectrometry, with concentrations reaching up to 1018 atoms/cm3 near the seed (top region) of the grown crystals. These results are compared with the theoretically predicted boron segregation profile calculated using the Scheil–Pfann equation. Additionally, the structural quality of the crystals was examined by using etch pit density measurement and X-ray diffraction techniques, including synchrotron white-beam X-ray topography and X-ray rocking curve imaging. It is shown that variations in boron concentrations in the 0–0.5 solidified fractions (g) of the grown crystals lead to a strain field along the growth direction. Finally, the feasibility and challenges of growing heavily boron-doped germanium crystals from the melt while maintaining a single crystallinity with a low dislocation density are discussed.