Effect of silicon spacer thickness on the electroluminescence of multilayer structures with self-assembled Ge(Si)/Si(001) islands

The results of investigation of the electroluminescence of multilayer $p$–$i$–$n$ structures with Ge(Si)/Si(001) self-assembled islands are presented. The nonmonotonic dependence of the room-temperature intensity of the electroluminescence signal from islands on the Si spacer thickness is revealed. The highest electroluminescence signal intensity is observed for structures with a Si spacer thickness of 15–20 nm. The significant decrease detected in the electroluminescence signal from the islands in structures with thick Si spacers ($>$ 20 nm) is explained by the formation of defect regions in them. The observed decrease in the electroluminescence signal in structures with thin Si layers is associated with a decrease in the Ge fraction in the islands in these structures, which is caused by enhanced Si diffusion into islands with increasing elastic strains in the structure.