B-Doped δ-Layers and Nanowires from Area-Selective Deposition of BCl3 on Si(100)

Atomically precise, delta-doped structures forming electronic devices in Si have been routinely fabricated in recent years by using depassivation lithography in a scanning tunneling microscope (STM). While H-based precursor/monatomic resist chemistries for incorporation of donor atoms have dominated these efforts, the use of halogen-based chemistries offers a promising path toward atomic-scale manufacturing of acceptor-based devices. Here, B-doped delta-layers were fabricated in Si(100) by using BCl3 as an acceptor dopant precursor in ultrahigh vacuum. Additionally, we demonstrate compatibility of BCl3 with both H and Cl monatomic resists to achieve area-selective deposition on Si. In comparison to bare Si, BCl3 adsorption selectivity ratios for H- and Cl-passivated Si were determined by secondary ion mass spectrometry depth profiling (SIMS) to be 310(10):1 and 1529(5):1, respectively. STM imaging revealed that BCl3 adsorbed readily on bare Si at room temperature, with SIMS measurements indicating a peak B concentration greater than 1.2(1) x 10(21) cm(-3) with a total areal dose of 1.85(1) x 10(14) cm(-2) resulting from a 30 langmuir BCl3 dose at 150 degrees C. In addition, SIMS showed a delta-layer thickness of similar to 0.5 nm. Hall bar measurements of a similar sample were performed at 3.0 K, revealing a sheet resistance of rho(rectangle) = 1.9099(4) k Omega rectangle(-1), a hole carrier concentration of p = 1.90(2) x 10(14) cm(-2), and a hole mobility of mu = 38.0(4) cm(2) V-1 s(-1) without performing an incorporation anneal. Finally, 15 nm wide B d-doped nanowires were fabricated from BCl3 and were found to exhibit ohmic conduction. This validates the use of BCl3 as a dopant precursor for atomic-precision fabrication of acceptor-doped devices in Si and enables development of simultaneous n- and p-type doped bipolar devices.

Automated summary

Atomically precise delta-doped structures in Silicon have been fabricated using BCl3 as an acceptor dopant precursor, showing compatibility with both H and Cl monatomic resists for area-selective deposition. The adsorption selectivity ratios for BCl3 on H- and Cl-passivated Si were determined, revealing promising results for potential atomic-scale manufacturing of acceptor-based devices. Measurements and characterization of BCl3-doped nanowires and delta-layers demonstrated the feasibility and effectiveness of using BCl3 for atomic-precision fabrication of electronic devices in Silicon.