GeAs as a novel arsenic dimer source for n-type doping of Ge grown by molecular beam epitaxy

Abstract

GeAs is successfully applied as a new arsenic dimer source for efficient n-type doping of Ge grown by molecular beam epitaxy. The arsenic fluxes emanating from GeAs Knudsen cells are not composed of arsenic tetramers, but only of arsenic dimers. High electron concentrations of up to 1.1×1020 cm−3 are achieved with GeAs, which is much larger than any ever obtained in antimony-doped Ge. The electron concentration in the arsenic-doped Ge films depends on the GeAs cell temperature with an activation energy of 2.5 eV, which coincides with that of the arsenic dimer beam flux generated from GeAs. Moreover, it is found that the electron and arsenic concentrations in the arsenic-doped Ge layer are identical. These results indicate that arsenic atoms are incorporated into Ge from the arsenic dimer beam, and that a very high electrical activation of the incorporated arsenic atoms is obtained.