Tunable spin and charge transport using CMOS-compatible silicon quantum dots for quantum information applications

Abstract

Scaling in commercially available silicon (Si) complementary-metal-oxide-semiconductor (CMOS) devices has inevitably led to single carrier behaviour exhibited at low temperatures owing to the strong orbital quantization of disorder based quantum dots (QDs). As a consequence, p-type Si metal-oxide-semiconductor-field-effect-transistors (MOSFETs) fabricated and supplied by Hitachi provide an excellent platform to evaluate and explore a plethora of rich phenomena that arise from the interplay of single hole transport and spin interactions. Through the use of the well terminal acting as a pseudo-gate in a MOSFET, I discover the formation of a double-QD system exhibiting Pauli spin blockade and investigate the magnetic field dependence of the leakage current. This enables attributes that are key to hole spin state control to be determined, where I calculate a tunnel coupling t_c of 57 µeV and a short spin-orbit length l_SO of 250 nm. The outcome of a strong spin-orbit interaction at the interface when using disorder based QDs demonstrates support for electric-field mediated control. In addition, I experimentally investigate the impact of electrical stress on the tunability of single hole transport properties in a MOSFET device. This is achieved by monitoring Coulomb-blockade from three disorder based QDs at the channel-oxide interface, which are known to lack tunability as a result of their stochastic origin. My findings indicate that when applying gate biases between -4 V to -4.6 V, nearby charge trapping enhances Coulomb-blockade leading to a stronger QD confinement that can be reversed to the initial device condition after performing a thermal cycle reset. Re-applying stress then gives rise to a predictable response from reproducible changes in the QD charging characteristics with consistent charging energy increases of up to ≈ 50% being observed. A threshold is reached above gate biases of -4.6 V, where the performance and stability become reduced due to device degradation occurring as a product of large-scale trap generation. These results not only suggest stress as an effective technique to enhance and reset charging properties, but also offer insight on how industry compatible Si devices can be harnessed for single charge transport applications by investigating interactions which are useful for quantum information processing.

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Identifiers

ORCID for Joseph, William Hillier: orcid.org/0000-0003-4418-0819

ORCID for Shinichi Saito: orcid.org/0000-0003-1539-1182

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