Detached growth of gallium doped germanium

Detached Bridgman growth of gallium-doped germanium itself as well as the transition from detached to attached growth was observed in-situ for the first time, using a quartz-glass ampoule in a mirror furnace. Crystal diameter was 9 mm, the growth length 41 mm, and the growth velocity 0.5 mm/min. Undoped 111-oriented germanium served as seed material; the melt was doped with gallium (C-0 = 8.2 x 10(18) at/cm(3)). Detachment took place after a growth length of 7 mm and continued for 27 mm; the remaining 7 mm. grew with wall contact again. The wall-free growth could be observed around the entire circumference except for some small bridges (width: a few tens of micrometers, length: some hundreds of micrometers), where the crystal grew in contact with the wall. In the detached-grown part of the crystal, the 111-related growth lines are clearly visible. The transition from attached to detached growth and vice versa did not take place along a straight fine but transitioned as islands over a length of about I mm. The gap between the growing crystal and the container wall varied between 10 and 80 mum, as measured by a profilometer. The etch pit density is greatly reduced in the part of the crystal that grew free of the wall. An increase in the EPD is seen in the area where the crystal had contact with the ampoule wall by the bridges described above. (C) 2002 Elsevier Science B.V. All rights reserved.