Enhanced structural and electronic properties of strained Ge(100) films grown by molecular-beam epitaxy with a Sb surfactant layer

Abstract

Reflection high-energy electron diffraction and angle-resolved photoemission spectroscopy with synchrotron radiation were used to investigate the effect of a Sb surfactant layer on the growth and electronic properties of strained Ge(100) films. The Ge epilayers were grown by molecular-beam epitaxy on highly ordered InP(100) substrates. The Ge/InP interface was found to be nonreactive yet extensive with outdiffusion of In into the overlayer. With a Sb surfactant layer the critical thickness for a coherently strained Ge film was increased to 5 ML, which is 2.5 times larger than the critical thickness for Ge films grown without a surfactant. The experimental values for the valence-band offsets for epilayers under 2.9% tensile strain were found to be ΔEv = −0.94 ± 0.1 eV and ΔEv = −0.97 ± 0.1 eV for films grown with and without a surfactant layer, respectively. These results are in agreement with the model-solid theoretical prediction of ΔEv = −1.00 eV for this strained heterostructure.