Comparative analysis of luminescence properties of Ge : Sb layers grown on Ge(001) and Si(001) substrates

Comparative studies of the luminescent properties of Sb doped Ge layers grown on Si (001) and Ge (001) substrates have been carried out. It is shown that in Ge:Sb/Ge(001) layers, in contrast to the Ge:Sb layers grown on silicon, indirect optical transitions make a significant contribution to the photoluminescence signal. This fact is associated with a longer lifetime of charge carriers in homoepitaxial Ge:Sb/Ge structures due to the absence of crystal lattice defects associated with the relaxation of elastic strain. It is shown that the significant increase in the contribution of direct optical transitions to the total photoluminescence signal observed at higher doping levels of Ge:Sb/Ge(001) layers is caused by an increase in the population of electronic states in the $\Gamma$ valley. The luminescent properties of Ge:Sb/Ge(001) and Ge:Sb/Si(001) layers with Sb concentration significantly exceeding its equilibrium solubility are strongly affected by the nonradiative recombination centers, which may be clusters of impurity atoms.