Enhanced emission of Ge nanoislands in two-dimensional photonic crystals with an unpatterned central region

Two-dimensional photonic crystals are widely used to enhance the light-emitting properties of active media, primarily due to improved light extraction efficiency. However, it is well known that the formation of photonic crystals introduces additional non-radiative recombination centers, which hinders the positive effect of photonic crystals on luminescence efficiency. In this study, we fabricated light-emitting structures with self-assembled Ge nanoislands embedded in different types of two-dimensional PhCs, such as conventional uniform PhCs, PhCs with an unpatterned central region, and so-called “random PhCs.” Using various micro-PL spectroscopy techniques, we conducted a comparative study of the obtained PhCs with high spectral, temporal, and spatial resolutions. It has been shown that the formation of specially designed PhCs with an unpatterned central region enables a light extraction efficiency comparable to that of uniform PhCs owing to the effective interaction of the emitted photons with the PhC modes. Moreover, by reducing the non-radiative recombination of charge carriers in the unpatterned region, such PhCs provide an additional increase in the overall emission intensity in the 1.3–1.6 μm spectral range. The obtained results can be used for further development of near-IR light sources for Si-based photonic integrated circuits.