Recent studies of SiGeSn materials and optoelectronic devices hold great promise for photonics integrated circuits (PICs) on Si platform featuring scalable, cost-effective, and power-efficient. Thanks to the breakthrough of low temperature material growth techniques, device-quality level materials have been grown, following by the demonstration of light-emitting diodes, photodetectors, and optically pumped and electrically injected band-to-band lasers. While the exciting developments in bulk devices were reported, the quantum wells (QWs) have been investigated targeting the dramatically improved and/or novel device performance via variety of quantum confinement effects. In this review, we summarize the recent progress on development of SiGeSn QWs, including the fundamental optical and transition studies and optoelectronic device applications. The inspirational results reveal the possibility of all-group-IV PICs with photonics and electronics monolithically integrated on a single-chip.

We report on the connection between strain, composition, defect density and the photoluminescence observed before and after annealing at 300 °C for GeSn samples with Sn content of 8% to 10%. Results show how the composition and level of strain influenced the separation between the indirect and direct optical transitions, while changes in the level of strain also influenced the density of misfit dislocations and surface roughness. The effect of annealing is observed to lower the level of strain, decreasing the energy separation between the indirect and direct optical transitions, while also simultaneously increasing the density of misfit/threading dislocations and surface roughness. The reduction in energy separation leads to an increase of photoluminescence (PL) emission, while the increase of misfit/threading dislocations density and surface roughness results in a decrease of PL. Consequently, the competition between these factors is observed to determine the impact of annealing on the PL. As a result, annealing increases the collected PL for small (≤40 meV) separation between the indirect to direct optical transitions in the as-grown sample while decreases the PL for larger (≥60 meV) separations. More generally, these numbers have a small dependence on the level of strain in the as-grown samples.

GeSn-based quantum wells are of great interests for the development of all-group-IV optoelectronic devices such as lasers. Using a GeSn buffer and SiGeSn barrier has been studied with the aim of obtaining a direct bandgap well and increasing the carrier confinement. However, the carrier collection efficiency with such a configuration remains unsatisfactory. In this work, a single quantum well with additional GeSn barrier inserted between the GeSn well and the SiGeSn barrier was grown and characterized. Under relatively low carrier injection, the photoluminescence results show dramatically enhanced emission from the quantum well compared to the reference samples with only SiGeSn barrier, indicating a significantly improved carrier collection efficiency of the well.

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As one of two mainstream platforms, photonics integrated circuits (PICs) on Si photonics platform benefits from the mature complementary metal-oxide-semiconductor (CMOS) manufacturing capabilities and allows for the processing of Si-based PICs with ultra-high volume and low cost. Recent studies of SiGeSn materials, which yield true direct bandgap with sufficient Sn incorporation, hold great promise for PICs featuring scalable, cost-effective, and power-efficient. While the exciting developments in bulk devices including lasers, light emitting diodes (LEDs), and photodetector were reported, the quantum wells (QWs) structure and devices have been investigated targeting the dramatically improved and/or novel device performance via variety of quantum confinement effects. In this work, we report the recent progress on SiGeSn QW development. Particularly, the study of MQW laser is presented. Devices with higher optical confinement factors exhibit clear lasing confirmed by the threshold characteristic and the emission spectra below and above threshold. Only spontaneous emission was observed with the thinner cap layer samples. On the other hand, samples with thicker cap layers of 250 and 290 nm exhibit clear lasing at 77 K with thresholds of 214 and 664 kW/cm 2 , respectively. These promising results establish the guidance for the device design and pave the way for the SiGeSn QW devices towards future high-performance PICs on Si platform.