Zuechtung von defektarmen dotierten und undotierten GaAs-Einkristallen mit dem vertikalen Gradient-Freezing-Verfahren Kurze Darstellung der Ergebnisse und Abschlussbericht

Abstract

Multi zone furnaces, automation concepts and laboratory technologies have been developed using the Vertical Gradient Freeze technique for single crystal growth of GaAs with the aim to produce a low dislocation density. The crystallization prozess is performed by an electronically controlled temperature field without moving the furnace or the sample. A command variables generator free programable yields the temperature time programs for the fully automatized growth process. On the basis of a complex process simulation the crystal growth rate, the As partial pressure as well as the temporal and local temperature gradients could be adjusted with high precision and optimized by systematic growth experiments. The crystals grown are characterized by dislocation densities up 1 to 3 x 10"3 cm"-"2, a large area cellular structure and a low density of microdefects. Si-doped and semi-insulating crystals with reproducible physical properties were grown both in (100) and (111) orientation, respectively. The possibility of affecting the crystal properties by post-growth annealing was shown experimentally. (orig.)SIGLEAvailable from TIB Hannover: F95B346+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Forschung und Technologie (BMFT), Bonn (Germany)DEGerman