Ge-Based Nanowires of Metastable Composition: Hyper-Doping and Alloy Formation

This contribution will address the formation of nanowires and nanorods of metastable composition and demonstrate the significant changes in physical properties associated with their composition.[1] All the growth studies are carried out either in solution or by gas phase techniques using the metal to be incorporated in the Ge host lattice as a growth seed. This approach allowed the formation of highly crystalline, metastable Ge_1-yGa_y (y~0.03%) as well as Ge_1-xSn_x (x=0.13-0.28) nanowires and nanorods at low temperatures.[2-4] The materials have been characterized by different analytical methods including TEM, EDX, Raman spectroscopy as well as XRD. Generally, a homogeneous incorporation of unusually high contents of Sn and Ga in the Ge lattice has been observed. The high incorporation efficiency also alters the physical properties significantly. While hyperdoped Ge_0.97Ga_0.03 shows quasi-metallic behavior in temperature dependent transfer characteristics, Ge_0.81Sn_0.19 reveals still semiconducting behavior in equivalent experiments. Moreover, the formation of Ge_1-xSn_x with x&gt;0.09 causes the transformation to a direct bandgap material, while the solid solubility limit according to the binary phase diagram (~ 1 at% Sn in Ge) has to be overcome. The efficient absorption and emission in the mid-IR range (&lt;~0.55 eV) makes Ge_1-xSn_x very attractive for CMOS-compatible optoelectronics based purely on group IV elements. The high crystal quality of CVD-grown, epitaxial Ge_0.81Sn_0.19 nanowires can be illustrated.<br/><br/><br/><i>References </i><br/>[1] <i>Chem. Mater.</i> <b>2020</b>, <i>32,</i> 2703-2741<br/>[2] ACS Nano <b>2018,</b> 12, 1236.<br/>[3] Chem. Mater. <b> 2017</b>, <i>29</i>, 9802.<br/>[4^]ACS Nano <b>2019</b>,<i> 13, </i>8047