Electroluminescence studies of Er and SiO co-doped Si layers prepared by molecular beam epitaxy

Abstract

Er/O co-doped Si light emitting diodes (LEDs) have been fabricated using layer structures prepared by molecular beam epitaxy (MBE). The Er/O doping was realized by sublimation of elemental Er and silicon monoxide simultaneously with Si during MBE growth. Intense Er-related electroluminescence (EL) at 1.54 μm was observed at room temperature from p +-SiGe/i-SiGe-Si/Si:Er/n +-Si LEDs by electron impact excitation under reverse bias. It has been found that the EL intensity was increased with increasing growth temperature of the Si:Er/O layer in the range of 430–575°C. The electrical pumping power dependence of EL intensity has been studied. An excitation cross section value of ∼1×10 −16 cm 2 was estimated based on the experimental data and model fitting. The EL decay behavior under various injection and bias conditions has been studied by time-resolved EL measurements. The overall luminescence decay time is found to strongly depend on the injection parameters. Two types of de-excitation mechanisms due to Auger energy transfer to free carriers introduced by either dopant ionization or carrier injection have been discussed. Both Auger processes play an important role in reduction of the EL intensity when there is a high density of carriers with excited Er ions.