Sharp interface of undoped Ge/SiGe quantum well grown by ultrahigh vacuum chemical vapor deposition

An undoped Ge/SiGe quantum well has been grown by ultrahigh vacuum chemical vapor deposition, and the sharp interface with a characteristic length of 0.6 nm is confirmed by cross-sectional transmission electron microscopy and electron energy loss spectroscopy. In addition, a 2D hole gas with a high mobility of up to 4.6 × 105 cm2/V s is achieved in the Hall-bar shaped field effect transistor, showing a low percolation density of 8.7 × 1010 cm−2, a light hole effective mass of 0.071 m0, and a high effective g-factor of 11.3. These favorable properties confirm the benefits of high-quality interface, which has promising applications in the field of qubits.