Critical Factors in the Growth of Hyperdoped Germanium Microwires by Electrochemical Liquid–Liquid–Solid Method

Factors that affect crystalline growth of germanium (Ge) micro- and nanowires by the electrochemical liquid–liquid solid (ec-LLS) method in water have been identified. Alloys of gallium and indium (Ga1–xInx) were used as liquid metal microdroplet electrodes in ec-LLS to determine whether the resultant conductivity of as-grown Ge could be strongly modulated by adjusting the fraction of Ga. Current–potential measurements on individual microwires were performed as a function of alloy composition. All alloys of Ga and In yielded Ge microwires with low resistivity and showed evidence of metal incorporation beyond the solubility limit (i.e., hyperdoping). The observed Ge crystal growth rates were insensitive to the alloy composition. In contrast, lowering the concentration of GeO2 dissolved in solution and/or increasing the density of droplets noticeably slowed down the microwire growth rate. Cumulatively, these data help define what parameters should be useful in refining the ec-LLS method to produce materials with specific targeted properties.