Modifying germanium to achieve efficient light emission holds great potential in the field of silicon-based light sources. We propose a method of introducing stress by repeatedly etching trenches and filling them with silicon nitride (SiN). By combining germanium tin (GeSn) alloys with an external stress layer of SiN, efficient modification of germanium is achieved. We performed process and device simulations on the structure, and the results showed that ∼0.8 GPa of biaxial tensile stress was introduced into the active region of the light-emitting diode, with a peak wavelength of 2200 nm and a maximum photoelectric conversion efficiency of about 5%. The device structure we proposed provides an effective solution for realizing silicon-based integrated light sources.
Ge has become a focus in the development of optoelectronic devices integrated into silicon platforms due to its compatibility with standard complementary metal-oxide-semiconductor (CMOS) technology. To reduce the bandgap of Ge, thereby enhancing its optical properties and accelerating the development of CMOS-compatible silicon-based germanium light sources, we propose a strained Ge LED with a microbridge structure. By etching two isosceles triangles with opposite apexes on the Ge layer and utilizing the edge stress concentration, the ideal tensile strain is achieved at the edge of the microbridge. Simulation results show that the Ge LED exhibits a peak wavelength of 1960 nm and a maximum electrical-to-optical conversion efficiency of 1.6%. Finally, this single structure is expanded into a ring-shaped array to increase the area of stress concentration. Simulation results show that the Ge LED array exhibits a peak wavelength of 1790 nm and a maximum electrical-to-optical conversion efficiency of 1.45%.
The GePb alloys are formed by implanting of Pb into Ge with a Pb dose of 2×1015 cm-2 and 6×1015cm-2 , following with rapid thermal annealing at the temperature of 500°C and 600°C under N2 atmosphere. The root-mean-square roughness of the GePb sample with the implantation dose of 6×1015cm-2 annealed at 600°C is measured to be 1.10 nm characterized by using atomic force microscope in the 5μm×5um scan area, which is the smallest value among reported results. It can be observed from the TEM measurent results that the GePb thickness of the samples with the implantation dose of 2×1015cm-2 and 6×1015cm-2 are approximately 20 nm and 30 nm, respectively. Pb composition of these samples decrease with the increasing of the annealing temperature due to the full precipitation of Pb out of Ge in the film. Temperature-dependent Hall measurement shows that a high Hall mobility of around 230-260 cm2 /Vs has been achieved at the measurement temperature of 80K and this value drops to about 110 cm2 /Vs at 300K. However, these values are both higher than that of traditional Ge sample. These results indicates that GePb alloys is a promising high mobility channel material for the future integrated optoelectronic circuit application.
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