Silicon photonics is emerging as a competitive platform for electronic–photonic integrated circuits (EPICs) in the 2 µm wavelength band where GeSn photodetectors (PDs) have proven to be efficient PDs. In this paper, we present a comprehensive theoretical study of GeSn vertical p–i–n homojunction waveguide photodetectors (WGPDs) that have a strain-free and defect-free GeSn active layer for 2 µm Si-based EPICs. The use of a narrow-gap GeSn alloy as the active layer can fully cover entire the 2 µm wavelength band. The waveguide structure allows for decoupling the photon-absorbing path and the carrier collection path, thereby allowing for the simultaneous achievement of high-responsivity and high-bandwidth (BW) operation at the 2 µm wavelength band. We present the theoretical models to calculate the carrier saturation velocities, optical absorption coefficient, responsivity, 3-dB bandwidth, zero-bias resistance, and detectivity, and optimize this device structure to achieve highest performance at the 2 µm wavelength band. The results indicate that the performance of the GeSn WGPD has a strong dependence on the Sn composition and geometric parameters. The optimally designed GeSn WGPD with a 10% Sn concentration can give responsivity of 1.55 A/W, detectivity of 6.12 × 10¹⁰ cmHz^½W⁻¹ at 2 µm wavelength, and ~97 GHz BW. Therefore, this optimally designed GeSn WGPD is a potential candidate for silicon photonic EPICs offering high-speed optical communications.

We demonstrate an electrically-injected GeSn $\textit {p-i-n}$ waveguide light emitting diode on silicon, comprising a vertical Ge/GeSn/Ge double-barrier heterostructure for $2 ~\mu \text{m}$ wavelength band integrated photonics. The incorporation of 4.2% Sn into the GeSn active layer results in bandgap shrinkage and extends the operating range to 2200 nm. Our design of the double-barrier heterostructure with the waveguide provides good carrier and optical confinement. The electroluminescence spectra at different current injection densities were measured at room temperature, demonstrating the peak wavelength at 1962 nm with the cutoff at 2200 nm, covering the entire $2 ~\mu \text{m}$ wavelength band. The results show that the proposed vertical $\textit {p-i-n}$ heterostructure GeSn diode opens a pathway to meeting the demand for group IV-based light sources required for $2 ~\mu \text{m}$ wavelength band integrated photonics.

GeSn waveguide photodetectors (WGPDs) that function in the 2-µm band have been considered potentially competitive candidates for cryogenic silicon photonics to enable various emerging applications such as quantum sensing and quantum computing. Herein, we present a high-performance GeSn rib WGPD that can function within the 2-µm spectral range and its temperature-dependent characteristics. The proposed detectors feature a GeSn active layer with 4.9% Sn which redshifts the cutoff wavelength to cover the 2-µm band. In addition, the optical confinement factor was enhanced by growing a thick GeSn active layer. This resulted in a room temperature responsivity of 0.224 A/W at $\lambda = \text{1900 nm}$ . We measured a noise equivalent power of $9.5 \times {{10}^{ - 10}}\ \mathrm{W}/\mathrm{H}{{\mathrm{z}}^{1/2}}$ at $\lambda = \text{1550 nm}$ , confirming the practical viability of the proposed detector. Moreover, the temperature-dependent characteristics indicate that the dark current density ( ${{J}_{{\rm{dark }}}}$ ) variation is extremely low and responsivity decreases at low temperatures, leading to decreased spectral detectivity ( ${{D}^*}$ ), whereas the cut-off wavelength ( ${{\lambda }_{\mathrm{c}}}$ ) blueshifts owing to the increased bandgap. The temperature-dependent characteristics of the proposed GeSn WGPDs are expected to advance the understanding of GeSn WGPDs for cryogenic silicon photonics.

The pursuit of highly efficient mid-infrared (MIR) photodetectors (PDs) for electronic photonic integrated circuits (EPICs) has spurred extensive research, with GeSn alloys emerging as promising candidates due to their tunable bandgaps and compatibility with complementary metal-oxide-semiconductor (CMOS) processes. Herein, we present the first demonstration of vertical p-i-n GeSn ridge waveguide photodetectors (WGPD) exhibiting cutoff wavelength of λ = 2.61 μm suitable for MIR EPICs on Si. These WGPDs incorporate thick graded GeSn layers with 4.85% and 10.41% Sn content, achieving a narrow direct bandgap that facilitates efficient light absorption in the MIR range up to λ = 2.61 μm. A theoretical analysis using finite element method (FEM) simulation reveals optical confinement factors (OCF) of $\Gamma = 60.03\% $ and $\Gamma = 30.37\% $ for the 1^st and 2^nd i-GeSn layers, respectively, indicating enhanced light–matter interactions. Key parameters such as dark current, optical response, and specific detectivity $({{D}^*})$ are thoroughly discussed, providing insights into the functionality of these GeSn WGPDs operating in the MIR regime. The proposed device exhibits a room-temperature ${{D}^*}$ of ${{D}^*} = 3.05 \times {{10}^6}\;\text{cmH}{{\mathrm{z}}^{{\rm{1/2}}}}{{\mathrm{W}}^{{\rm{ - 1}}}}$ at λ = 2 μm, comparable to the operational range of commercially available E-InGaAs PD, affirming its versatility across MIR applications. The integration of the proposed WGPD into EPICs opens avenues for advanced operations in the MIR region, with potential applications across diverse industries and scientific fields that require MIR photodetection capabilities.

We report high-performance germanium-on-insulator (GeOI) waveguide photodetectors (WGPDs) for electronic–photonic integrated circuits (EPICs) operating at telecommunication wavelengths. The GeOI samples were fabricated using layer transfer and wafer-bonding techniques, and a high-quality Ge active layer was achieved. Planar lateral p-i-n WGPDs were fabricated and characterized, and they exhibited a low dark current of 0.1 µA. Strain-induced alterations in the optical properties were observed, resulting in an extended photodetection range up to λ = 1638 nm. This range encompasses crucial telecommunication bands. The WGPDs exhibited a high responsivity of 0.56 A/W and a high detectivity of D^∗ = 1.87 ×10⁹cmHz^1/2W ^{- 1} at 1550 nm. A frequency-response analysis revealed that increasing the bias voltage from −1 to −9 V enhances the 3-dB bandwidth from 31 to 49 MHz. This study offers a comprehensive understanding of GeOI WGPDs, fostering high-performance EPICs with implications for telecommunications and beyond.

Silicon photonics is emerging as a competitive platform for electronic-photonic integrated circuits (EPICs) at the 2 µm wavelength band where GeSn photodetectors (PDs) have proven to be efficient PDs. Here, we present a comprehensive theoretical study of GeSn vertical p-i-n homojunction waveguide photodetectors (WGPDs) that have a strain-free and defect-free GeSn active layer for 2-µm Si-based EPICs. The use of a narrow-gap GeSn alloy as the active layer can fully cover entire the 2 µm wavelength band. The waveguide structure allows for decoupling the photon-absorbing path and the carrier-collection path, thereby allowing for simultaneous achievement of high-responsivity and high-bandwidth (BW) operation at the 2-µm wavelength band. We present the theoretical models to calculate the carrier saturation velocities, optical absorption coefficient, responsivity, 3-dB bandwidth, zero-bias resistance, and detectivity, and optimize this device structure to achieve highest performance at the 2-µm wavelength band. The results indicate that the performance of the GeSn WGPD has strong dependence on the Sn composition and geometric parameters. The optimally designed GeSn WGPD with 10% Sn concentration can give responsivity of 1.55 A/W, detectivity of 6.12×1010 cmHz½W-1 at 2 µm wavelength, and ~97 GHz BW. Therefore, this optimally designed GeSn WGPD is a potential candidate for silicon photonic EPICs offering high-speed optical communications.