Abstract: A process for producing nitrogen-doped semiconductor wafers has the nitrogen being derived from a dopant gas which contains NH3. The process includes pulling a single crystal from a melt of molten semiconductor material, feeding the dopant gas to the semiconductor material, and cutting the nitrogen-doped semiconductor wafers off the pulled single crystal. The dopant gas is fed to the semiconductor material at most until pulling begins for that part of the single crystal from which the semiconductor wafers are cut.

Abstract: A method and a device is provided for determining the diameter of a monocrystal growing at a crystallization boundary during the pulling of the monocrystal from a melt. The method includes imaging a part of the crystallization boundary on at least one mirror, observing the mirror image and determining the diameter of the monocrystal from the observed relative position of the crystallization boundary on the mirror image.

Abstract: Device for making monocrystalline gallium arsenide by drawing the crystal from a gallium arsenide-containing melt with adjustment of an arsenic vapor pressure while rotating and lifting the drawing means, said device comprising means for rotating the crucible containing an uncovered melt, and if desired, lifting or lowering the crucible independently of the system, that is to say without rotating the entire quartz apparatus. The means for rotating the crucible includes a ground-in joint formed by the core of the crucible driving shaft and a quartz glass sleeve. The core is made of a material havinga higher coefficient of expansion than quartz glass at the operating temperature of the joint. The accurate seating of the ground-in joint avoids the formation of surface waves on the melt.