Lasing in direct-bandgap GeSn alloy grown on Si

Large-scale optoelectronics integration is limited by the inability of Si to emit light efficiently1, because Si and the chemically well-matched Ge are indirect-bandgap semiconductors. To overcome this drawback, several routes have been pursued, such as the all-optical Si Raman laser2 and the heterogeneous integration of direct-bandgap III–V lasers on Si3,4,5,6,7. Here, we report lasing in a direct-bandgap group IV system created by alloying Ge with Sn8 without mechanically introducing strain9,10. Strong enhancement of photoluminescence emerging from the direct transition with decreasing temperature is the signature of a fundamental direct-bandgap semiconductor. For T ≤ 90 K, the observation of a threshold in emitted intensity with increasing incident optical power, together with strong linewidth narrowing and a consistent longitudinal cavity mode pattern, highlight unambiguous laser action11. Direct-bandgap group IV materials may thus represent a pathway towards the monolithic integration of Si-photonic circuitry and complementary metal–oxide–semiconductor (CMOS) technology. ISSN:1749-4885 ISSN:1749-4893