Davide Degli Esposti

We grow $^{28}$Si/SiGe heterostructures by reduced-pressure chemical vapor deposition and terminate the stack without an epitaxial Si cap but with an amorphous Si-rich layer obtained by exposing the SiGe barrier to dichlorosilane at 500 $^{\circ}$C. As a result, $^{28}$Si/SiGe heterostructure field-effect transistors feature a sharp semiconductor/dielectric interface and support a two-dimensional electron gas with enhanced and more uniform transport properties across a 100 mm wafer. At T = 1.7 K we measure a high mean mobility of (1.8±0.5)×$10^5$ cm$^{2}$/Vs and a low mean percolation density of (9 ± 1) × $10^{10}$ cm$^{−2}$. From the analysis of Shubnikov–de Haas oscillations at T = 190 mK we obtain a long mean single particle relaxation time of (8.1 ± 0.5) ps, corresponding to a mean quantum mobility and quantum level broadening of (7.5 ± 0.6) × $10^{4}$ cm$^{2}$/Vs and (40±3) μeV, respectively, and a small mean Dingle ratio of (2.3±0.2), indicating reduced scattering from long range impurities and a low-disorder environment for hosting high-performance spin-qubits.