This paper reports on lasing in a direct bandgap GeSn alloy grown on silicon (Si). The study addresses the challenge of silicon's indirect bandgap, which limits its use in optoelectronics. The researchers demonstrate lasing in a direct bandgap group IV semiconductor, GeSn, grown on Si(001) substrates. The GeSn alloy is grown using a reduced pressure chemical vapor deposition (CVD) process, with Sn concentrations up to 12.6%. The alloy exhibits a direct bandgap, as evidenced by photoluminescence (PL) measurements showing a fundamental direct bandgap with the Γ-valley 28 meV below the indirect L-valley. The study also shows that the GeSn layer has a low density of threading dislocations and mild compressive strain, indicating high crystalline quality. The researchers performed temperature-dependent PL measurements, revealing a significant increase in PL intensity with decreasing temperature, which is characteristic of a direct bandgap semiconductor. The PL intensity was found to be linearly related to the excitation power, indicating dominant band-to-band recombination. The study also demonstrates optical gain and lasing in the GeSn layer, with a threshold excitation density of approximately 325 kW/cm². The lasing is achieved using a Fabry-Perot cavity formed by the waveguide structure, with a clear threshold in output intensity. The lasing operates at temperatures up to 90 K, which coincides with the activation temperature for Shockley-Read-Hall recombination. The study highlights the potential of GeSn as a direct bandgap semiconductor for monolithic integration with silicon photonic circuits and complementary metal-oxide semiconductor (CMOS) technology. The results suggest that GeSn could be a promising material for future silicon-based optoelectronic devices. The research also discusses the challenges in achieving a direct bandgap in GeSn, including the low equilibrium solubility of Sn in Ge and the large lattice mismatch between Ge and α-Sn. The study concludes that GeSn could be a viable alternative to III-V materials for silicon-based lasers, offering the potential for cost-effective integration of electronic and photonic circuits.This paper reports on lasing in a direct bandgap GeSn alloy grown on silicon (Si). The study addresses the challenge of silicon's indirect bandgap, which limits its use in optoelectronics. The researchers demonstrate lasing in a direct bandgap group IV semiconductor, GeSn, grown on Si(001) substrates. The GeSn alloy is grown using a reduced pressure chemical vapor deposition (CVD) process, with Sn concentrations up to 12.6%. The alloy exhibits a direct bandgap, as evidenced by photoluminescence (PL) measurements showing a fundamental direct bandgap with the Γ-valley 28 meV below the indirect L-valley. The study also shows that the GeSn layer has a low density of threading dislocations and mild compressive strain, indicating high crystalline quality. The researchers performed temperature-dependent PL measurements, revealing a significant increase in PL intensity with decreasing temperature, which is characteristic of a direct bandgap semiconductor. The PL intensity was found to be linearly related to the excitation power, indicating dominant band-to-band recombination. The study also demonstrates optical gain and lasing in the GeSn layer, with a threshold excitation density of approximately 325 kW/cm². The lasing is achieved using a Fabry-Perot cavity formed by the waveguide structure, with a clear threshold in output intensity. The lasing operates at temperatures up to 90 K, which coincides with the activation temperature for Shockley-Read-Hall recombination. The study highlights the potential of GeSn as a direct bandgap semiconductor for monolithic integration with silicon photonic circuits and complementary metal-oxide semiconductor (CMOS) technology. The results suggest that GeSn could be a promising material for future silicon-based optoelectronic devices. The research also discusses the challenges in achieving a direct bandgap in GeSn, including the low equilibrium solubility of Sn in Ge and the large lattice mismatch between Ge and α-Sn. The study concludes that GeSn could be a viable alternative to III-V materials for silicon-based lasers, offering the potential for cost-effective integration of electronic and photonic circuits.