Electrically Detected Magnetic Resonance of Neutral Donors Interacting with a Two-Dimensional Electron Gas

Abstract

We have measured the electrically detected magnetic resonance of channel-implanted donors in silicon field-effect transistors in resonant X-(9.7 GHz) and W-band (94 GHz) microwave cavities, with corresponding Zeeman fields of 0.35 T and 3.36 T, respectively. It is found that the conduction electron resonance signal increases by two orders of magnitude from X-to W-band, while the hyperfine-split donor resonance signals are enhanced by over one order of magnitude. We rule out a bolometric origin of the resonance signals, and find that direct spin-dependent scattering between the two-dimensional electron gas and neutral donors is inconsistent with the experimental observations. We propose a new polarization transfer model from the donor to the conduction electrons as the main contributer to the spin resonance signals observed.Electrical spin-state detection for solid-state qubits requires a detection channel formed by conduction electrons in close proximity to the qubit. For electron spin qubits, the detection channels usually consist of quantum point contacts or single electron transistors, which are sensitive to the electrostatic environment nearby and able to detect the spin-dependent occupancies of electrons at the qubit site [1][2][3][4]. Alternatively, for nuclear spin qubits such as shallow donors in silicon [5], it was proposed that conduction electrons interacting directly with the neutral donors can be used for nuclear spin-state readout [6], as the conduction and neutral donor electrons undergo spindependent scattering [7][8][9][10][11]. Donor-doped metal-oxidesemiconductor (MOS) devices provide an ideal platform for the detection of such an interaction, as the electronic wavefunction of neutral donors embedded in the device channel can overlap with the nearby gate-induced twodimensional electron gas (2DEG) (Fig. 1(a)). The donor-2DEG interaction can be probed by electrically detected magnetic resonance (EDMR) experiments with the MOS system, as was first reported by Ghosh and Silsbee [7]. However, the use of bulk-doped silicon with a relatively high donor concentration resulted in significant overlap between the donor and 2DEG electron resonance signals, complicating the analysis of the results. In addition, their measurements were limited to a low magnetic field of ∼ 0.35 T. In this Letter, we clarify the mechanisms behind the EDMR signals of such donordoped MOS devices by studying the change in EDMR signal intensities at different magnetic fields. We perform EDMR with accumulation-mode n-type field-effect * Both authors contributed to this work equally. Please contact the corresponding author under cclo@eecs.berkeley.edu.

Electrically detected spin echoes of donor nuclei in silicon

“…A pulsed photoexcitation scheme could be utilized to enable readout only when required, retaining longer coherence times useful for computing and storage otherwise. Utilizing a MOSFET structure [27][28][29] would also allow this modification, as well as providing more accurate control of the donor density (and thus scattering time between free and donor electrons) which could be used to tune the nuclear spin lifetime 30 .…”

Large-scale atomistic density functional theory calculations of phosphorus-doped silicon quantum bits

“…Such detailed microscopic calculations will allow more accurate and detailed device simulations than are currently possible. By understanding the effects of modulations in the doping density including effects of both the spin density as well as the doping potential, allows now calculations which probe the readout properties of the qubits, especially using techniques such as EDMR [34,35,[53][54][55]. Additionally, alternative qubits such as excited-state dopants [59] or charged dopant qubits [57,[60][61][62] can now be explored with this accurate picture of the electronic structure.…”

“…These potentials also provide input for calculations of the cross sections of electron scattering at the dopants [51,52], which are largely determined by integrals of the doping density [51]. By calculating the scattering of conduction electrons confined in a two-dimensional layer located at a given distance from the (001) plane, a connection can be made with electrically detected magnetic resonance (EDMR) schemes [34,35,[53][54][55] used to measure the dopant spin state. Doping potentials calculated using atomistic DFT can also be used to parameterize new tight binding models, or effective single-electron models which more accurately reproduce the effects of the dopant electronic structure than standard effective mass models.…”

“…[33] and [16]), the accuracy of the description of dopant electronic structure contributes to these discrepancies. Additionally, electrically detected magnetic resonance (EDMR) [34] has called into question a theoretical picture of the scattering of electrons in a two-dimensional electron gas (2DEG) from dopants in silicon [35,36]. An ab initio description of a dopant in silicon is therefore useful both as a benchmark and for determining the details of the electronic structure of an isolated dopant which can subsequently be used to calculate more accurate spin-dependent scattering cross sections.…”

“…[33] and Refs. [30][31][32][33][34][35][36][37][38][39][40] therein) show a large amount of disagreement for calculated properties such as the valley splitting. Although some of this disagreement can be attributed to geometrical effects of dopant placement which we will not explore in detail (see instead Refs.…”