AlCl₃-Dosed Si(100)-2 × 1: Adsorbates, Chlorinated Al Chains, and Incorporated Al

Abstract

The adsorption of AlCl 3 on Si(100) and the effect of annealing the AlCl 3 -dosed substrate were studied to reveal key surface processes for the development of atomic-precision, acceptor-doping techniques. This investigation was performed via scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculations. At room temperature, AlCl 3 readily adsorbed to the Si substrate dimers and dissociated to form a variety of species. Annealing the AlCl 3 -dosed substrate at temperatures below 450 °C produced unique chlorinated aluminum chains (CACs) elongated along the Si(100) dimer row direction. An atomic model for the chains is proposed with supporting DFT calculations. Al was incorporated into the Si substrate upon annealing at 450 °C and above, and Cl desorption was observed for temperatures beyond 450 °C. Al-incorporated samples were encapsulated in Si and characterized by secondary ion mass spectrometry (SIMS) depth profiling to quantify the Al atom concentration, which was found to be in excess of 10 20 cm −3 across a ∼2.7 nm-thick δ-doped region. The Al concentration achieved here and the processing parameters utilized promote AlCl 3 as a viable gaseous precursor for novel acceptor-doped Si materials and devices for quantum computing.

Dopant Precursor Adsorption into Single-Dimer Windows: Towards Guided Self-Assembly of Dopant Arrays on Si(100)

“…The other selected precursors are being explored as candidates for atomically precise acceptor-doping applications. 23,24 The findings presented here indicate that SDW adsorption and the formation of well-ordered adsorbate arrays are energetically favorable with minor reaction barriers, supporting the idea of ordering dopants with guided self-assembly.…”

Reaction pathways of BCl$_3$ for acceptor delta-doping of silicon

“…This reaction pathway significantly resembles the previously elucidated pathway for AlCl 3 , although the reaction barriers are ≈0.3 eV higher. 21 Overall, the reaction pathway is both straightforward in contrast with similar reaction pathways for PH 3 and B 2 H 6 , 30,41 and thermodynamically downhill. This pathway implies that if sufficient thermal energy is applied, a BCl 3 molecule can adsorb and move into a stable bridging configuration with no obstacles.…”

“…[11][12][13] However, the pursuit of APAM-compatible acceptor doping has gained interest for creating bipolar electronic devices, 14 enabling qubits with high intrinsic spin-orbit coupling, [15][16][17] and the possibility of creating superconducting regions within Si. 4,[18][19][20] Recent work has explored a variety of potential APAM-compatible acceptor precursors such as diborane (B 2 H 6 ), 14 aluminum trichloride (AlCl 3 ), 21 boron trichloride (BCl 3 ), 22 and organics such as trimethyl and triethyl aluminum 23 . Additionally, several solution-based approaches have been explored.…”

Atomic-precision advanced manufacturing for Si quantum computing

“…There has been significant and accelerating progress over the past 10 years. Recent state-of-the-art developments include the following: (1) near deterministic atomic control of doping in all three dimensions; [28][29][30] (2) 3D devices with top gates aligned to buried structures; 28,30 (3) alternative dopants -acceptors (B 31 , Al 32 ) and a donor (As 33 ); and (4) alternative resist chemistries (halogens) that take APAM into vacuum (> 10 -8 torr) found in conventional Si foundries (see Fig. 3).…”

“…Recently, significant work aims to expand APAM to achieve acceptor doping comparable to current donor methods. 31,32…”