Silicon quantum dot devices with a self-aligned second gate layer

Abstract

We implement silicon quantum dot devices with two layers of gate electrodes using a selfalignment technique, which allows for ultrasmall gate lengths and intrinsically perfect layer-to-layer alignment. In a double quantum dot system, we investigate hole transport and observe current rectification due to Pauli spin blockade. Magnetic field measurements indicate that hole spin relaxation is dominated by spin-orbit interaction, and enable us to determine the effective hole g-factor 1.6. From an avoided singlet-triplet crossing, occurring at high magnetic field, the spin-orbit coupling strength 0.27 meV is obtained, promising fast and all-electrical spin control.

Electrical control of the g tensor of the first hole in a silicon MOS quantum dot

“…The g-tensor is the key parameter for studying the coupling of a spin-orbit state to a magnetic field [27][28][29][30][31][32][33][34] . However, most studies of the gtensor of hole quantum dots have been performed using devices that confine an unknown number of holes [35][36][37][38][39][40][41][42] . This has hindered the ability to understand hole spin-qubit devices, since the number of holes is a primary factor influencing the orbital physics of the quantum dot 43 .…”

Hole spin qubits in Si FinFETs with fully tunable spin-orbit coupling and sweet spots for charge noise

“…In this context, we find that Silicon Fin Field Effect Transistors (FinFETs) [50][51][52] are not only appealing because of their compatibility to modern semiconductor industry, but they naturally present operational sweet spots where charge noise completely vanishes. In these devices, the spin-orbit interactions can be exactly switched off at finite values of the electric field, and thus FinFET qubits are ideal candidates to reliably store quantum information.…”

“…A similar suppression of charge noise can occur when the wire is grown along different directions. For example, convenient sweet spots appear in Silicon-on-Insulator (SOI) FinFETs [50] or hut-wires [28] when the wire extends along the [110] direction, the standard growth direction used in experiments [28,46,51,52]; in this case, however, the spin-orbit interactions away from the sweet spots tend to be smaller.…”

“…By analysing the response of different state-of-the-art FinFET designs [50][51][52] to realistic electric fields with an inhomogeneous profile, we identify qualitatively distinct mechanisms that can switch off the spin-orbit interactions. When the triangular cross-section of the fin has a side larger than ∼ 35 nm, the intrinsic spinorbit interactions are cancelled out by a conventional direct Rashba-like component [21,22] that is driven by a homogeneous electric field perpendicular to the substrate and that is easily generated in FinFETs.…”

“…We focus on both SOI and bulk FinFETs. In SOI FinFETs, the charge noise sweet spot is restored by appropriately squeezing the fin and pushing the hole wavefunction towards the apex of the fin, or by growing the wire along the [110] direction, as standardly done in experiments [28,46,51,52], and pushing the holes towards the bottom of the fin. In bulk FinFETs, the Si substrate below the wire tends to decrease the spin-orbit interactions, but at the same time it re-establishes the spin-orbit sweet spot even when the fin is small.…”