Electrodeposition of crystalline germanium thin films by the electrochemical liquid-liquid-solid method

Abstract

The direct electrodeposition of crystalline germanium thin films in aqueous solutions at low temperatures represents a promising and cost-effective method for synthesising semiconductor materials. This study investigates the influence of the deposition potential and time on the characteristics of crystalline germanium thin films derived from germanium oxide precursors in aqueous solution through electrochemical liquid–liquid-solid (ec-LLS) process at low temperature. Additionally, it establishes a Ge/Cu Schottky junction by heterogeneous growth of germanium films on copper (Cu) metal via electrochemical liquid–liquid-solid–solid (ec-LLSS) process.X-ray diffraction (XRD) analysis revealed that an increase in the deposition potential to −1.7 V resulted in a shift in the crystal orientation of the germanium film from (220) to (111), while excessive deposition potential (>−2.0 V) led to a reduction in the crystallinity of the deposited samples. At a deposition temperature of 70 °C and a deposition potential of −1.8 V, the crystal cluster size and the crystal quality increased with the increasing deposition time. However, at −2.0 V, the crystallinity of the germanium film reached an optimal state after 30 min and then gradually declined with time.Charactersation techniques such as EDS, XPS and Raman spectroscopy indicated that the use of liquid electrode Ga(l) as a doping source during the electrodeposition process allowed for heterogeneous growth of Ga-doped p-type germanium films on a Cu substrate.The I-V characteristic curves demonstrated that the Ge/Cu Schottky junctions exhibited significant rectification characteristics, rendering them suitable for potential applications in solar cells.