Vertical Gradient Freeze (VGF)
VGF systems are designed for producing monocrystalline compound semiconductor crystals with minimal defect density as well as Gallium-Arsenide (GaAs), Indium-Phosphide (InP) and Gallium-Phosphide (GaP) crystals used in optoelectronics (LED and laser systems), semiconductor technology, high-frequency technology, solar technology and telecommunications technology. The method is also known as “Directional Solidification” or, in a similar form, as the “Bridgman Method.” The method is also used in the R&D sector.
The Process
Using a resistance heater, the polycrystalline raw material is heated up in a crucible with a seed crystal on the base and melted. The temperature zone is set so that the raw material first melts in the crucible. The seed crystal partly melts, too. The temperature zone is then moved relative to the crucible. This can be done either by moving the crucible or heater by mechanical means or by changing the temperature zone by controlling the various heater elements. The gradual cooling of the melt initially in the lower area initiates crystal growth in the crucible as the melt freezes. The heated zone slowly moves upward, which means that the solidification front slowly moves upward as well. The crystallization rate depends on how quickly the temperature zone is moved.
This method allows the industrial production of crystals such as Gallium Arsenide (GaAs), Indium Phosphide (InP) and Gallium Phosphide (GaP). These crystals are used in optoelectronics (LED and laser systems), semiconductor technology, high-frequency technology, solar technology and telecommunications technology.
Applications
Our modular “Kronos” system helps industrial companies to cultivate highly productive compound semiconductor crystals such as GaAs, InP, Germanium and CaF2.
The MultiCrystallizer allows multicrystalline ingot production for the photovoltaics industry.