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.

GeSn alloys hold great promise as high-performance, low-cost, near- and short-wavelength infrared photodetectors with the potential to replace the relatively expensive and currently market-dominant InGaAs- and InSb-based photodetectors. In this Letter, we demonstrate room-temperature GeSn pn photodetectors fabricated by a complementary metal-oxide-semiconductor compatible process, involving Sn and P ion implantation and flash-lamp annealing prior to device fabrication. The fabrication process enables the alloying of Ge with Sn at concentrations up to 4.5% while maintaining the high-quality single-crystalline structure of the material. This allows us to create Ge0.955Sn0.045 pn photodetectors with a low dark current density of 12.8 mA/cm2 and a relatively high extended responsivity of 0.56 A/W at 1.71 μm. These results pave the way for the implementation of a cost-effective, scalable, and CMOS-compatible short-wavelength infrared detector technology.

We have investigated the recrystallization behavior of the argon (Ar) bubble-rich amorphous germanium (a-Ge) by utilizing the excimer laser annealing (ELA) in comparison with the conventional furnace annealing (FA). We demonstrate that the ELA can efficiently suppress the Ar bubbles to have good recrystallization of a-Ge in sharp contrast to the conventional FA treatment where the bubble-rich a-Ge can only be getting partial recrystallization with many dislocations and stacking faults. Transmission electron microscopy results exhibit that ELA can transform the Ar implantation-induced damaged layer into a fully crystalline matrix containing no visible defects except isolated bubbles in a low density. We reveal the critical role of the Ar bubbles played in the recrystallization behavior of the a-Ge by comparing the two types of annealing methods. This finding provides a new routine to suppress the implantation-induced noble-gas bubbles in semiconductors to solve the issue of the high-quality regrowth of the noble–gas implanted layer.

The first-principles calculations have recently shown that implanting sufficient noble gas atoms into germanium (Ge) can expand its lattice to achieve the desired tensile strain for indirect-to-direct bandgap transition to develop the on-chip high-efficient light emitter. Here, to experimentally prove this strain-doping concept, we implant argon (Ar) ions into Ge and then recrystallize the Ar-doped amorphous Ge (a-Ge) layer using nanosecond laser annealing (NLA) and furnace thermal annealing (FTA), respectively. The NLA effectively recrystallizes the 12 nm thick a-Ge layer with minimal loss of Ar dopants, while FTA fails to fully recrystallize it and results in significant loss of Ar dopants. The regrown Ge layer with Ar concentration above the critical value (0.8%) for bandgap transition is 3.8 nm thick, making it a challenge to distinguish the photoluminescence signal of strain-doped layer from the substrate. To overcome this, increasing the implantation energy and adding a capping layer may be necessary to further prevent Ar loss and achieve a strain-doped layer with sufficient depth. These findings provide promising view of the strain-doping concept for direct-bandgap emission from Ge.

Incorporating lead (Pb) into the germanium (Ge) lattice emerges as a promising approach for bandgap engineering, enabling luminescence at longer wavelengths and paving the way for enhanced applications in short-wave infrared (SWIR) light sources and photodetectors. In this work, we report on optical properties of GePb alloys fabricated by a complementary metal-oxide semiconductor (CMOS)-compatible process that includes Pb ion implantation followed by solid-phase epitaxial regrowth via flash-lamp annealing. Optical characterization, including photoluminescence spectroscopy and Fourier-transform infrared reflectance spectroscopy, reveals that GePb alloys exhibit a reduced bandgap compared to pure Ge, resulting in longer-wavelength emission, while also providing broadband antireflective properties below 1800 nm wavelengths due to the surface subwavelength nanostructure. These findings position nanostructured GePb as a highly promising candidate for SWIR optoelectronic applications.