In this Letter, we demonstrate mid-infrared (MIR) lateral p − i − n GeSn waveguide photodetectors (WGPDs) on silicon, to the best of our knowledge for the first time, as a key enabler of MIR electronic–photonic integrated circuits (EPICs). Narrow-bandgap GeSn alloys were employed as the active material to enable efficient photodetection in the MIR region. A lateral p − i − n homojunction diode was designed and fabricated to significantly enhance the optical confinement factor of the guided modes and thus enhance the optical responsivity. Thus, a photodetection range of up to 1950 nm and a good responsivity of 0.292 A/W at 1800 nm were achieved. These results demonstrate the feasibility of planar GeSn WGPDs for monolithic MIR EPICs on silicon.

We report an investigation of a planar GeSn p–i–n diode for a high-detectivity photodetector based on an undoped GeSn film. By fabricating n- and p-type regions on the plane of the GeSn film using the complementary metal–oxide–semiconductor technology of ion implantation, a low dark current density is revealed and attributed to the low defect density of the film and current flow suppression around the diode periphery. This yields a specific 1550-nm detectivity of ∼1010 cm Hz1/2 W−1, an order of magnitude higher than that of conventional vertical GeSn-based diodes and comparable to that of commercially available Ge-based diodes. This work provides an alternative approach for achieving a high-detectivity GeSn photodetector that may facilitate its potential applications.

Recombination of photogenerated electron–hole pairs dominates the photocarrier lifetime and then influences the performance of photodetectors and solar cells. In this work, we report the design and fabrication of band-aligned van der Waals-contacted photodetectors with atomically sharp and flat metal–semiconductor interfaces through transferred metal integration. A unity factor α is achieved, which is essentially independent of the wavelength of the light, from ultraviolet to near-infrared, indicating effective suppression of charge recombination by the device. The short-circuit current (0.16 μA) and open-circuit voltage (0.72 V) of the band-aligned van der Waals-contacted devices are at least 1 order of magnitude greater than those of band-aligned deposited devices and 2 orders of magnitude greater than those of non-band-aligned deposited devices. High responsivity, detectivity, and polarization sensitivity ratio of 283 mA/W, 6.89 × 1012 cm Hz1/2 W–1, and 3.05, respectively, are also obtained for the device at zero bias. Moreover, the efficient suppression of charge recombination in our air-stable self-powered photodetectors also results in a fast response speed and leads to polarization-sensitive performance.

The application of strain into GeSn alloys can effectively modulate the band structures, thus creating novel electronic and photonic devices. Raman spectroscopy is a powerful tool for characterizing strain; however, the lack of Raman coefficient makes it difficult for accurate determination of strain in GeSn alloys. Here, we have investigated the Raman-strain function of Ge1-xSnx along <1 0 0> and <1 1 0> directions. GeSn nanomembranes (NMs) with different Sn compositions are transfer-printed on polyethylene terephthalate (PET) substrates. External strain is introduced by bending fixtures with different radii, leading to uniaxial tensile strain up to 0.44%. Strain analysis of flexible GeSn NMs bent along <1 0 0> and <1 1 0> directions are performed by Raman spectroscopy. The linear coefficients of Raman-strain for Ge0.96Sn0.04 are measured to be −1.81 and −2.60 cm -1 , while those of Ge0.94Sn0.06 are decreased to be −2.69 and −3.82 cm -1 along <1 0 0> and <1 1 0> directions, respectively. As a result, the experimental ratio of linear coefficient (ROLC) of Ge, Ge0.96Sn0.04 and Ge0.94Sn0.06 are 1.34, 1.44 and 1.42, which agree well with theoretical ROLC values calculated by elastic compliances and phonon deformation potentials (PDPs). In addition, the compositional dependence of PDPs is analyzed qualitatively. These fundamental parameters are important in designing high performance strained GeSn electronic and photonic devices.

We demonstrate room-temperature, mid-infrared resonant electroluminescence from GeSn resonant-cavity LEDs with a lateral p-i-n configuration on a silicon-on-insulator substrate. A vertical cavity to enhance light emission in the GeSn active layer is formed by the low-index buried oxide and deposited SiO 2 layer. A planar lateral p-i-n diode structure favorable for CMOS-compatible, dense integration was designed and fabricated for current injection. Under continuous-wave electrical injection, room-temperature resonant electroluminescence was successfully observed at ∼ 1980    nm with a spectral emission factor of 2.2. These results could pave the way toward efficient electrically injected GeSn light emitters operating at room temperature.