Impact of quantum well thickness on hole mobility in strained germanium heterostructures

Germanium (Ge) and silicon (Si), group IV semiconductors, as innovative epitaxial structures, continue to offer improved properties and enhanced parameters for applications in classical and quantum electronics as well as spintronics. The mobility of free carriers is one such parameter that defines the ultimate performance of electronic devices. The dependence of two-dimensional hole gas (2DHG) mobility on 2DHG density in an undoped gate controlled compressively strained Ge quantum well (QW) grown on Si (cs-GoS), with QW thicknesses of 15 and 30 nm, is studied and compared at T = 0.3 K. Experimental results show that 2DHG mobility is higher in the thinner QW. 2DHG mobilities of 3.1 × 106 and 1.55 × 106 cm2 V−1 s−1 are measured in 15 and 30 nm QWs, respectively, with the same carrier density of 0.9 × 1011 cm−2. The results are explained by the existing theory of carriers' scattering on background ionized impurities.