Controlling Nucleation and Crystal Growth of Ge in a Liquid Metal Solvent

Abstract

The electrochemical liquid–liquid–solid (ec-LLS) deposition of crystalline germanium (Ge) in a eutectic mixture of liquid gallium (Ga) and indium (In) was analyzed as a function of liquid metal thickness, process temperature, and flux. Through control of reaction parameters, conditions were identified that allow selective nucleation and growth of crystalline Ge at the interface between e-GaIn and a crystalline Si substrate. The crystal growth rates of Ge by ec-LLS as a function of process temperatures were obtained from time-dependent powder X-ray diffraction measurements of crystalline Ge. The driving force, Δμ, for crystal formation in ec-LLS was estimated through analyses of the experimental data in conjunction with predictions from a finite-difference model. The required Δμ for Ge nucleation was tantamount to a supersaturation approximately 102 larger than the equilibrium concentration of Ge in e-GaIn at the investigated temperatures. These points are discussed both in the context of advancing new, lo...