Demonstration of mm long nearly intrinsic GeSn single-crystalline wires on quartz substrate fabricated by nucleation-controlled liquid-phase crystallization

Abstract

Millimeter long GeSn wires were fabricated on quartz substrates by using an advanced rapid melt growth method, named “nucleation-controlled liquid-phase crystallization” (NCLPC). Local melting of amorphous GeSn wires surrounded by SiO2 capping layers led to the propagation of single crystal growth from the solid/liquid interface without any crystal seeds and catalysts. Slow cooling just after rapid melting was beneficial in NCLPC for prolonged and stable lateral growth, and 1.7 mm long single-crystalline GeSn wires were successfully demonstrated. Physical characterizations revealed that, since excessive Sn atoms were swept out toward the growth direction, a mostly uniform GeSn single crystal, in terms of Sn content and crystallinity, was formed along the wires. Electrical measurements of top-gate MOSFETs with NCLPC-GeSn channels revealed the formation of nearly intrinsic GeSn single crystal, indicating a significant reduction in acceptor-like point defects achieved with the slow-cooling procedure.