Electrical activation and electron spin resonance measurements of implanted bismuth in isotopically enriched silicon-28

Abstract

We have performed continuous wave and pulsed electron spin resonance measurements of implanted bismuth donors in isotopically enriched silicon-28. Donors are electrically activated via thermal annealing with minimal diffusion. Damage from bismuth ion implantation is repaired during thermal annealing as evidenced by narrow spin resonance linewidths (Bpp = 12 µT) and long spin coherence times (T2 = 0.7 ms, at temperature T = 8 K). The results qualify ion implanted bismuth as a promising candidate for spin qubit integration in silicon.Electron and nuclear spins of donor atoms in silicon are excellent qubit candidates for quantum information processing [1, 2]. Isotope engineered substrates provide a nuclear spin free host environment, resulting in long electron and nuclear spin coherence times of several seconds [3,4]. Spin properties of donor qubit candidates in silicon have been studied mostly for phosphorous and antimony [3][4][5][6]. Bismuth donors in silicon are unique in exhibiting a relatively large zero field splitting of 7.4 GHz. Thus, they have attracted attention as potential nuclear spin memory and spin qubit candidates [7,8] that could be coupled to superconducting resonators [7,9,10]. Bismuth is the deepest donor in silicon with a binding energy of 70 meV and a corresponding small Bohr radius. The small Bohr radius and bismuth's reduced effective gyromagnetic ratio [7] can make it less susceptible to interface noise at a given implant depth and make bismuth very desirable for quantum logic implementation via magnetic dipolar coupling [11]. Furthermore, bismuth is also the heaviest donor in silicon and thus shows the least ion range straggling during ion implantation, which enables for donor qubit placement with high spatial resolution [12,13].To date, studies of spin resonance properties of bismuth in silicon have been performed with bulk doped natural silicon [7,8,[14][15][16] whereas silicon-28 material is preferable for improved spin coherence properties. Electrical activation of implanted bismuth via thermal anneals has been studied for relatively high implant doses [17][18][19][20][21], and concentrations close to the the metalinsulator transition (N c = 1.7 × 10 19 cm −3 ) [18]. High implant doses ( 1 × 10 14 cm −2 for keV Bi-ions at room temperature) amorphize the silicon lattice [22]. Solid- * Please contact the corresponding author under cdweis@lbl.gov phase epitaxial regrowth (SPER) can be used to prevent diffusion of bismuth atoms and incorporate them on substitutional sites. This can lead to electrically active concentrations well above the low relatively solubility limit of bismuth in silicon (which is, e.g. 2.3 × 10 17 cm −3 at 1150 ℃ [23]). For SPER, thermal anneals at low temperatures, e.g. few minutes at 600 ℃ yield electrical activation levels of up to 90 % [20]. For low implant doses and dopant concentrations, which are desirable for long spin coherence times, no amorphization of the silicon crystal occurs during ion implantation. Thus, the electrical activation levels and annealing ...

Magnetic Resonance with Squeezed Microwaves

“…More details on the characterization of this sample can be found in Refs. [38,39]. Figure 5(b) shows this spin resonance line, obtained by measuring the spin-echo intensity as a function of the magnetic field B 0 (with SQZ off).…”

Hyperfine Stark effect of shallow donors in silicon

“…TB and BMB, though, are computationally demanding numerical approaches, which eclipse full physical understanding. Current theoretical predictions of hyperfine shifts, then, are limited to Si:P alone, but other V group donors such as Bi are now established as promising alternative donor qubits and are being widely researched [29][30][31][32][33]. We are thus motivated to present a multi-valley EMT that provides a unifying framework for P, As, Sb and Bi donors.…”

Decoherence mechanisms of209Bi donor electron spins in isotopically pure28Si

“…It begs the question, however, of whether other donors of the same group, i.e. arsenic (As), antimony (Sb) and bismuth (Bi), could have the same if not better properties than P. As the deepest group V donor, Bi has the largest nuclear spin (9/2) and the largest hyperfine coupling (1.4754 GHz) [6], and has received increasing attention over the past two years [7][8][9][10][11]. A single donor has a 20 dimensional Hilbert space, allowing either more storage space or a more robust encoding of information.…”