Monolayer doping of germanium by phosphorus-containing molecules

Area of Science:

• Materials Science
• Surface Chemistry
• Semiconductor Doping

Background:

• Germanium (Ge) doping is crucial for advanced semiconductor devices.
• Monolayer doping (MLD) offers precise control over dopant incorporation.
• Understanding precursor adsorption is key to MLD process development.

Purpose of the Study:

• To investigate diethyl 1-propylphosphonate (DPP) and octadecylphosphonic acid (ODPA) as precursors for Ge MLD.
• To analyze the adsorption behavior and physicochemical interactions of these molecules on Ge surfaces.
• To evaluate phosphorus diffusion and doping effectiveness using different annealing methods.

Main Methods:

• Surface adsorption studies of DPP and ODPA on germanium.
• Quantitative phosphorus analysis using surface-sensitive techniques.
• Investigation of phosphorus diffusion via thermal annealing and pulsed laser melting.

Main Results:

• DPP adsorbs on oxidized Ge, forming 2-4 monolayers; ODPA chemisorbs on -H terminated Ge, forming a single monolayer.
• Conventional thermal annealing is ineffective for phosphorus diffusion into Ge due to high activation energy.
• Pulsed laser melting enables effective Ge doping via precursor decomposition under UV light.

Conclusions:

• DPP and ODPA exhibit distinct adsorption mechanisms on Ge surfaces.
• Pulsed laser melting is a viable technique for monolayer doping of germanium with phosphorus.
• The findings provide insights into optimizing MLD processes for germanium.