Plasmon-Phonon Coupling in Electrostatically Gated β-Ga₂O₃ Films with Mobility Exceeding 200 cm² V^-1 s^-1

Area of Science:

• Materials Science
• Condensed Matter Physics
• Semiconductor Physics

Background:

• Monoclinic β-Ga2O3 is an ultra-wide bandgap semiconductor with significant research interest.
• Fundamental studies of plasmon-phonon coupling in β-Ga2O3 are hindered by difficulties in achieving high carrier densities without chemical disorder.

Purpose of the Study:

• To investigate the impact of plasmon-phonon coupling on electron transport properties in β-Ga2O3.
• To achieve tunable carrier densities in β-Ga2O3 films via electrostatic doping.
• To understand the dynamic screening effects influencing electron mobility.

Main Methods:

• Fabrication of ion-gel-gated electric double-layer transistors for β-Ga2O3 films.
• Temperature-dependent Hall effect measurements.
• Transport modeling and ab initio calculations of electron-phonon scattering rates.

Main Results:

• Achieved highly reversible, electrostatic doping of β-Ga2O3 with tunable carrier densities.
• Observed a peak room-temperature mobility of 201 cm² V⁻¹ s⁻¹, followed by a decrease with increasing carrier density due to plasmon-phonon coupling.
• Identified an "antiscreening" effect arising from dynamic screening by hybrid plasmon-phonon modes.

Conclusions:

• Plasmon-phonon coupling significantly influences electron mobility in β-Ga2O3, exhibiting an antiscreening effect.
• Higher room-temperature mobility (up to 300 cm² V⁻¹ s⁻¹) is theoretically possible at high electron densities (>10²⁰ cm⁻³).
• Understanding plasmon-phonon coupling is crucial for enhancing mobility in Ga2O3 and other polar semiconductors for device applications.