Characterization of 4 in VGF-GaAs single crystals grown in a heater-magnet module

Silicon-doped 4 in VGF-GaAs single crystals were grown under the influence of traveling magnetic fields (TMF). A ${\stackrel{}{\mathit{}}}^{}$ heater-magnet module (HMM) was used for the simultaneous generation of heat and TMF through a combination of DC and AC control. In this study, we investigated changing structural and electronical properties as well as micro- and macrosegregation of VGF-GaAs single crystals grown with applied TMF.

Striations were observed in crystals grown without or too strong TMF. Almost no micro-inhomogeneities were detected when the magnetic flux densities of the TMF were matched to progression of solidification. With utilized TMF, induced melt flow opposed natural convection driven by buoyancy forces. Axial dopant incorporation was enhanced through a reduction of flow velocities and converging melt flow towards the center of the solid–liquid interface. The radial segregation profiles were flattened through a reduction of the concave deflection. While low frequency TMF bended the interface center more convex, the effect of high frequency TMF was more limited to the melt periphery. Furthermore, with large high frequency TMF current shares the impact of the minor three-dimensional asymmetric magnetic field distribution in the HMM became more relevant. Consequently, the application of double-frequency TMF led to a reduction of etch pit density through reduction of interface concavity.