Carrier mobility is one of the most important parameters of any semiconductor material, determining its suitability for applications in a large variety of electronic devices including field effect transistors (FETs). Bulk or 3D, Germanium (Ge), with its very high intrinsic hole and electron mobilities of 1900 and 3900 cm²V^-1s^-1 at room temperature, respectively, is the most promising candidate material to replace Si channels in future complementary metal oxide semiconductor (CMOS) devices. When one or more of the dimensions of a solid are reduced sufficiently to nanometer range, its physicochemical characteristics notably depart from those of the bulk solid. With reduction in size, novel electrical, mechanical, chemical, magnetic, and optical properties can be introduced. The resulting structure is then called a low-dimensional structure or system.

Biaxial compressive strain in nm scale thick Ge epilayer narrows its band gap and causes the appearance of a quantum well (QW) in the valence band. Holes confined in the strained Ge QW form a two-dimensional hole gas (2DHG) and have an increased mobility due both to their lower effective mass and reduced scattering factors in this material system. During the recent years a major breakthrough have been achieved in enhancement of carrier mobility in strained epitaxial Ge grown on a standard Si(001) substrate. Extremely high room- and low-temperature 2DHG mobilities of up to 4,500 cm²V^-1s^-1 and 1,500,000 cm²V^-1s^-1, respectively, have been demonstrated. These hole mobilities are the highest not only among the group-IV Si, SiGe, Ge, SiC and Diamond semiconductors, but also among p-type III–V, II–VI and emerging 2D materials.

The 2DHG mobilities in strained Ge are already sufficiently high to fabricate sub-100 nm electronic devices and demonstrate ballistic transport therein at or around room temperature. This material will be an excellent platform for scientists to discover new quantum phenomena and applications.