Growth of Zn-doped germanium under microgravity

The doping of germanium with zinc from a remote, temperature-stabilized sou rce was studied under microgravity. A nominally undoped Ge-crystal was grow n by the Gradient-Freeze technique with the melt surface being in permanent contact with a gaseous atmosphere of zinc. The dopant and carrier concentr ations in the solidified Germanium were measured by SIMS, Hall and resistan ce measurements and compared with the results of a terrestrial reference ex periment as well as with concentration profiles calculated on the basis of the thermodynamics of the: growth system. The results prove the possibility of vapour phase doping under microgravity. Moreover, the Zn-concentration at the initial phase boundary even agrees well with the equilibrium value, strongly indicating a nearly homogeneous distribution of the dopant within the melt before the crystallization.