Electrical Transport Properties Driven by Unique Bonding Configuration in γ-GeSe

Area of Science:

• Materials Science
• Solid State Physics
• Condensed Matter Physics

Background:

• Group IV monochalcogenides possess diverse thermoelectric and ferroelectric properties.
• Electrical characteristics of these materials are highly dependent on the specific chalcogen element.
• Germanium telluride (GeTe) shows high doping, while sulfur/selenium-based compounds are semiconductors with notable band gaps.

Purpose of the Study:

• To investigate the electrical and thermoelectric properties of γ-GeSe, a newly identified polymorph of germanium selenide (GeSe).
• To understand the factors contributing to the distinct electrical behavior of γ-GeSe compared to other GeSe polymorphs.

Main Methods:

• Experimental measurements of electrical conductivity and Seebeck coefficient.
• Magnetoresistance measurements to probe electronic properties.
• First-principles calculations and elemental analysis to determine crystal structure and doping mechanisms.

Main Results:

• γ-GeSe exhibits high electrical conductivity (∼10^6 S/m) and a low Seebeck coefficient (9.4 μV/K) at room temperature.
• A high p-doping level (5 × 10^21 cm^-3) was observed, attributed to abundant germanium vacancies.
• Magnetoresistance data indicated weak antilocalization, suggesting significant spin-orbit coupling.

Conclusions:

• γ-GeSe represents a unique polymorph with significantly altered physical properties due to modified local bonding.
• The high p-doping concentration, driven by germanium vacancies, is a key factor in its distinct electrical conductivity.
• This discovery highlights the potential of exploring different polymorphs for tailored material properties.