In-situ Ga doping of fully strained Ge_(1-x)Sn_x heteroepitaxial layers grown on Ge(001) substrates

摘要

We have investigated the Ga and Sn content dependence of the crystallinity and electrical properties of Gadoped Ge_(1-x)Sn_x layers that are heteroepitaxially grown on Ge(001) substrates. The doping of Ga to levels as high as the solubility limit of Ga at the growth temperature leads to the introduction of dislocations, due to the increase in the strain of the Ge_(1-x)Sn_x layers. We achieved the growth of a fully strained Ge_(0.922)Sn_(0.078) layer on Ge with a Ga concentration of 5.5×10~(19) /cm~3 without any dislocations and stacking faults. The resistivity of the Ga-doped Ge_(1-x)Sn_x layer decreased as the Sn content was increased. This decrease was due to an increase in the carrier concentration, with an increase in the activation level of Ga atoms in the Ge_(1-x)Sn_x epitaxial layers being induced by the introduction of Sn. As a result, we found that the resistivity for the Ge_(0.950)Sn_(0.050) layer annealed at 600℃ for 1 min is 3.6 times less than that of the Ga-doped Ge/Ge sample.