Activation and electron spin resonance of near-surface implanted bismuth donors in silicon

Bi donors in Si are attractive for quantum computing due to their large Hilbert space and clock transitions. Qubit control, coupling, and readout by surface nanocircuitry requires a Bi depth of 20 nm---achievable using ion implantation. This work explores the electrical activation, substitutional fraction, and diffusion of near-surface implanted Bi with fluences above and below the Si amorphization threshold into both crystalline and preamorphized Si to find optimal annealing strategies. To demonstrate the successful activation and quantum control, the full hyperfine spectrum of near-surface Bi is obtained using electron spin resonance, supporting the suitability for Bi donor qubits.