Stretching the Equilibrium Limit of Sn in Ge1- x Sn x Nanowires: Implications for Field Effect Transistors

Subhajit Biswas; Jessica Doherty; Emmanuele Galluccio; Hugh G Manning; Michele Conroy; Ray Duffy; Ursel Bangert; John J Boland; Justin D Holmes

doi:10.1021/acsanm.0c02569

Stretching the Equilibrium Limit of Sn in Ge_{1- x} Sn _x Nanowires: Implications for Field Effect Transistors

ACS Appl Nano Mater. 2021 Feb 26;4(2):1048-1056. doi: 10.1021/acsanm.0c02569. Epub 2021 Feb 3.

Authors

Subhajit Biswas^{1

2}, Jessica Doherty^{1

2}, Emmanuele Galluccio², Hugh G Manning³, Michele Conroy⁴, Ray Duffy², Ursel Bangert⁴, John J Boland³, Justin D Holmes^{1

2}

Affiliations

¹ School of Chemistry and Advanced Materials and Bioengineering Research (AMBER) Centre, University College Cork, Cork T12 YN60, Ireland.
² Tyndall National Institute, University College Cork, Cork T12 R5CP, Ireland.
³ School of Chemistry and AMBER, Trinity College Dublin, Dublin 2, Ireland.
⁴ TEMUL, Department of Physics, Bernal Institute, University of Limerick, Limerick V94 T9PX, Ireland.

Abstract

Ge_1-x Sn _x nanowires incorporating a large amount of Sn would be useful for mobility enhancement in nanoelectronic devices, a definitive transition to a direct bandgap for application in optoelectronic devices and to increase the efficiency of the GeSn-based photonic devices. Here we report the catalytic bottom-up fabrication of Ge_1-x Sn _x nanowires with very high Sn incorporation (x > 0.3). These nanowires are grown in supercritical toluene under high pressure (21 MPa). The introduction of high pressure in the vapor-liquid-solid (VLS) like growth regime resulted in a substantial increase of Sn incorporation in the nanowires, with a Sn content ranging between 10 and 35 atom %. The incorporation of Sn in the nanowires was found to be inversely related to nanowire diameter; a high Sn content of 35 atom % was achieved in very thin Ge_1-x Sn _x nanowires with diameters close to 20 nm. Sn was found to be homogeneously distributed throughout the body of the nanowires, without apparent clustering or segregation. The large inclusion of Sn in the nanowires could be attributed to the nanowire growth kinetics and small nanowire diameters, resulting in increased solubility of Sn in Ge at the metastable liquid-solid interface under high pressure. Electrical investigation of the Ge_1-x Sn _x (x = 0.10) nanowires synthesized by the supercritical fluid approach revealed their potential in nanoelectronics and sensor-based applications.