Quantum and dielectric confinement on phosphorus donors in silicon nano-transistors for high-temperature single-electron tunneling

The intrinsically low tunnel barriers of conventional phosphorus-donors in bulk silicon preclude the observation of single-electron tunneling at practical temperatures. However, scaling devices to the nanometer dimensions introduces pronounced quantum and dielectric confinement effects, leading to elevated tunnel barriers. Here, we experimentally demonstrated strong confinement effects on three isolated donors located extremely close to the buried-oxide layer within a silicon-on-insulator nano-transistor channel region. Consequently, increased ionization-energies exceeding 100 meV are observed, which suggest confined donor potential with increased charging-energies, consistent with observed high-temperature Coulomb-oscillations. Such enhanced energy scales of isolated donors facilitate the room-temperature operation, even with a conventional donor such as phosphorus, which is corroborated by Coulomb-blockade simulations. These findings will boost up the advancement of the development of single-donor-based single-electron devices, bringing them closer to practical applications.