Influence of the growth conditions and doping level on the luminescence kinetics of Ge:Sb layers grown on silicon

The emission properties of Ge layers grown on Si(001) substrates and doped with Sb to different levels are studied by means of steady-state and time-resolved photoluminescence spectroscopy. It is shown that the peak of the steady-state photoluminescence intensity of $n$-Ge/Si layers at room temperature is observed at an Sb concentration close to the level of the equilibrium solubility of Sb in Ge ($\sim$10$^{19}$ cm$^{-3}$), which is in agreement with previously obtained results. Studies of the kinetics of photoluminescence associated with direct radiative transitions in Ge show that an effect on the kinetics is produced not only by the concentration of introduced donors, but also the conditions of formation, among them the deposition temperature of $n$-Ge layers. It is found that an increase in the Sb concentration results in a decrease in the charge-carrier lifetime. It is established that the low growth temperatures required to attain high doping levels in Ge layers also yield a substantial decrease in the charge-carrier lifetime compared to that in Ge layers produced at high temperatures. The conditions of short-term thermal annealing of the structures are determined, wherein the above-mentioned negative effects can be compensated, i.e., the photoluminescence intensity can be enhanced and the charge-carrier lifetime can be extended.