Dislocation- and crosshatch-free high-mobility silicon two-dimensional electron gases

Si/SiGe heterostructures play pivotal roles in both gate-all-around technology for integrated circuits and spin qubits for quantum computing. Here, we report dislocation-free Si/SiGe heterostructures grown via molecular beam epitaxy on strain-relaxed transferred SiGe films on Si (001) substrates. The transferred SiGe films, with dimensions of 2 × 2 mm2, are homogeneous and fully strain relaxed. No dislocations and crosshatches are detected in either the transferred SiGe films or the epitaxial heterostructures. The SiGe/Si/SiGe two-dimensional electron gas (2DEG) on such transferred films demonstrates a mobility up to 5.18 × 105 cm2 V−1 s−1, significantly surpassing prior reported values. In addition, a low percolation density of 5.83 × 1010 cm−2 indicates minimal disorder in the 2DEG, while a large Dingle ratio (∼30) reveals that background impurity scattering is the dominant factor limiting electron mobility.