Spectral and kinetic properties of radiation of self-assembled Ge(Si) nanoislands in two-dimensional photonic crystals with different hole depths

Subject of study . This study investigated SiGe heterostructures with self-assembled Ge(Si) nanoislands embedded in two-dimensional photonic crystals. Aim of study . The aim of the study was to determine the dependence of the spectral and temporal characteristics of the radiation of structures with Ge(Si) islands in two-dimensional photonic crystals on the depth of the holes forming the photonic crystal. Additionally, the characteristic decay times of the luminescence of islands in photonic crystals and the main mechanisms influencing their dependence on the etching depth of the photonic-crystal holes were determined. Method . The studied structures were obtained using molecular-beam epitaxy, electron-beam lithography, and plasma-chemical etching. The optical properties of the obtained structures were analyzed using microphotoluminescence spectroscopy with high spectral (0.5 nm) and temporal (50 ps) resolution. Main results . The dependences of the intensity, spectral shape, and characteristic decay times of the photoluminescence of self-assembled Ge(Si) islands in two-dimensional photonic crystals with a hexagonal lattice on the etching depth of the photonic-crystal holes were determined. The characteristic decay time of the luminescence of islands in the photonic crystals at room temperature decreased from 9 ns for the initial structure without photonic crystals to 0.6 ns for the sample with holes etched to the full depth of the grown structure (335 nm). This decrease is associated with an increase in the nonradiative recombination of charge carriers at the hole boundaries. The optimal ratio of the hole depth to the thickness of the active region of the structure was determined. Using this optimal ratio led to a maximum increase in the luminescence intensity of the Ge(Si) islands in two-dimensional photonic crystals compared with that of planar structures without photonic crystals. Practical significance . The obtained results are important for the development of efficient light sources in the near-infrared range for silicon-based integrated optoelectronics.