High Electron Mobility in Ge Films Grown on Si (001) by an 8-Inch Molecular Beam Epitaxy System

Area of Science:

• Materials Science
• Solid-State Physics
• Semiconductor Technology

Background:

• Silicon-based germanium (Ge) films are essential for next-generation low-power, high-performance electronics and optoelectronics.
• Directly growing high-quality Ge films on Si substrates presents significant challenges due to lattice mismatch and strain.
• Achieving high carrier mobility in Ge films is critical for device performance.

Purpose of the Study:

• To develop an effective method for directly growing Ge films with ultrahigh carrier mobility on Si (001) substrates.
• To characterize the structural properties and surface morphology of the grown Ge films.
• To evaluate the electrical properties, particularly carrier mobility, of the Ge films.

Main Methods:

• Utilized molecular beam epitaxy (MBE) for direct Ge film growth on Si (001) substrates.
• Employed techniques to manage strain relaxation through the formation of partial and misfit dislocations at the Ge/Si interface.
• Characterized film surface morphology using atomic force microscopy (AFM) and measured carrier mobility via Hall effect measurements.

Main Results:

• Successfully grew Ge films on Si (001) with a smooth surface (RMS roughness of 0.187 nm).
• Achieved a low threading dislocation density of 1.2 × 10⁷ cm^-2.
• Observed ultrahigh room-temperature carrier mobility up to 1916 cm²V^-1s^-1 with a carrier concentration of 1.425 × 10¹⁶ cm^-3.

Conclusions:

• The developed MBE approach enables the direct growth of high-quality Ge films on Si.
• The grown Ge films exhibit excellent structural properties and exceptionally high carrier mobility.
• These findings highlight the potential of MBE-grown Ge films for advanced electronic and optoelectronic device applications.