Holes Outperform Electrons in Group IV Semiconductor Materials

Area of Science:

• Materials Science
• Condensed Matter Physics
• Semiconductor Technology

Background:

• Achieving high charge carrier mobility is crucial for advancing semiconductor devices.
• Existing materials like strained silicon have limitations in charge carrier mobility.
• Germanium-based semiconductors offer potential for enhanced electronic properties.

Purpose of the Study:

• To report a record-high hole mobility in epitaxial strained germanium (s-Ge).
• To investigate the unique combination of properties in s-Ge for advanced electronics.
• To explore the potential of s-Ge for low-temperature and quantum electronics.

Main Methods:

• Development of state-of-the-art epitaxial growth technology for high-quality s-Ge.
• Growth of s-Ge on a standard silicon wafer.
• Measurement of hole mobility at 300 mK.

Main Results:

• Record-high hole mobility of 4.3 × 10^6 cm^2 V^-1 s^-1 achieved in s-Ge.
• Hole mobility in s-Ge is approximately twice that of electron mobility in strained silicon.
• s-Ge exhibits a large, tunable effective g*-factor (>18), low percolation density (5 × 10^9 cm^-2), and small effective mass (0.054 m0).

Conclusions:

• The developed s-Ge material platform demonstrates superior monocrystalline quality and low defect density.
• The unique combination of high mobility and other properties makes s-Ge a promising candidate for future electronic applications.
• This material is significant for developing low-temperature electronics with reduced Joule heating and spin qubit-based quantum circuits.