Monolayer Doping of Germanium with Arsenic: A New Chemical Route to Achieve Optimal Dopant Activation

Abstract

Reported here is a new chemical route for the wet chemical functionalization of germanium (Ge), whereby arsanilic acid is covalently bound to a chlorine (Cl)-terminated surface. This new route is used to deliver high concentrations of arsenic (As) dopants to Ge, via monolayer doping (MLD). Doping, or the introduction of Group III or Group V impurity atoms into the crystal lattice of Group IV semiconductors, is essential to allow control over the electronic properties of the material to enable transistor devices to be switched on and off. MLD is a diffusion-based method for the introduction of these impurity atoms via surface-bound molecules, which offers a nondestructive alternative to ion implantation, the current industry doping standard, making it suitable for sub-10 nm structures. Ge, given its higher carrier mobilities, is a leading candidate to replace Si as the channel material in future devices. Combining the new chemical route with the existing MLD process yields active carrier concentrations of dopants (>1 × 1019 atoms/cm3) that rival those of ion implantation. It is shown that the dose of dopant delivered to Ge is also controllable by changing the size of the precursor molecule. X-ray photoelectron spectroscopy (XPS) data and density functional theory (DFT) calculations support the formation of a covalent bond between the arsanilic acid and the Cl-terminated Ge surface. Atomic force microscopy (AFM) indicates that the integrity of the surface is maintained throughout the chemical procedure, and electrochemical capacitance voltage (ECV) data shows a carrier concentration of 1.9 × 1019 atoms/cm3 corroborated by sheet resistance measurements.

Study of the Molecule Adsorption Process during the Molecular Doping

“…These data will be discussed later, together with the carrier concentration profile measurements. While the presence of multi-layers and their removal from the top of the sample has been mentioned in many previous works [ 1 , 42 , 43 ], a deep investigation of the cleaning process effects on the molecule layers has not been done yet. In this work, the effects of surface cleaning on the molecule coverage have been investigated by cleaning a group of the produced samples right after the deposition step.…”

Grafting of Organophosphonic Acid Monolayers on Hydrogen-Terminated Silicon Surface and Secondary Functionalization in Supercritical Carbon Dioxide Media

“…The developed SCCO 2 process will allow more advanced studies on the OPA monolayer and its effect on the surface properties and charge transfer across the interface. The OPA grafted surface can be used for controlled nanoscale monolayer doping, 18,42,43 molecular electronics, and tuning the surface band structure for efficient charge transfer across the interface. 44 ■ ASSOCIATED CONTENT * sı Supporting Information…”

Exposing Cu(100) Surface via Ion-Implantation-Induced Oxidization and Etching for Promoting Hydrogen Evolution Reaction

“…Ion implantation technology is widely applied to surface doping and modification in the field of semiconductor fabrication and metal processing. − Furthermore, this technology is liable to create atomic vacancies through the kicked-out effect of the implanted ions. Therefore, we combined the ion implantation technology and electrochemical oxidation etching process to prepare a Cu self-supporting electrode with specific crystal planes.…”