Group IV materials provide a foundational platform for advancing silicon-based photonics applications. Especially, GeSn-based Group-IV alloys have demonstrated a direct band gap with higher electron mobility, which is beneficial for photonic integrated chips (PIC) and spintronic fields with complementary metal-oxide semiconductor (CMOS) compatibility.1 A recent breakthrough in the Si photonics field was the demonstration of continuous-wave, electrically pumped lasing based on advanced SiGeSn/GeSn multi-quantum well structures (MQWs).2 In addition, theoretical calculations predict that C substitution into the Ge and GeSn lattice further improves the fundamental bandgap directness, enhancing laser performance.3 Moreover, incorporating C as well as Si and Sn into Ge allowed a large tunability of the light emission in the Mid-infrared range of 2-5 μm. However, the low solid solubility and large lattice mismatch mostly limit the substitutional incorporation of C into the Ge diamond lattice.
Devaiya et al. (2025) studied this question.