It is known that self-assembled molecular monolayer doping technique has the advantages of forming ultra-shallow junctions and introducing minimal defects in semiconductors. In this paper, we report however the formation of carbon-related defects in the molecular monolayer-doped silicon as detected by deep-level transient spectroscopy and low-temperature Hall measurements. The molecular monolayer doping process is performed by modifying silicon substrate with phosphorus-containing molecules and annealing at high temperature. The subsequent rapid thermal annealing drives phosphorus dopants along with carbon contaminants into the silicon substrate, resulting in a dramatic decrease of sheet resistance for the intrinsic silicon substrate. Low-temperature Hall measurements and secondary ion mass spectrometry indicate that phosphorus is the only electrically active dopant after the molecular monolayer doping. However, during this process, at least 20% of the phosphorus dopants are electrically deactivated. The deep-level transient spectroscopy shows that carbon-related defects are responsible for such deactivation.

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Self-assembled molecular monolayer (SAMM) doping has great potential in state-of-the-art nanoelectronics with unique features of atomically precision and nondestructive doping on complex 3D surfaces. However, it was recently found that carbon impurities introduced by the SAMM significantly reduced the activation rate of phosphorus dopants by forming majority carrier traps. Developing a defect-free SAMM-doping technique with a high activation rate for dopants becomes critical for reliable applications. Considering that susbstitutional boron does not interact with carbon in silicon, herein we employ Hall measurements and secondary ion mass spectrometry (SIMS) to investigate the boron activation rate and then deep level transient spectroscopy (DLTS) and minority carrier transient spectroscopy (MCTS) to analyze defects in boron-doped silicon by the SAMM technique. Unlike the phosphorus dopants, the activation rate of boron dopants is close to 100%, which is consistent with the defect measurement results (DLTS and MCTS). Only less than 1% boron dopants bind with oxygen impurities, forming majority hole traps. Interestingly, carbon-related defects in the form of C s H and C s OH act as minority trap states in boron-doped silicon, which will only capture electrons. As a result, the high concentration of carbon impurities has no impact on the activation rate of boron dopants.

Rational design of electronic properties and geometric structure of carbon matrix is an effective strategy to develop high-performance carbon-based electrocatalysts toward oxygen reduction reaction. Herein, hollow carbon nanospheres are synthesized...

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Self-assembled molecular monolayer (SAMM) doping on semiconductors has been widely appraised for its advantages of doping nanoelectronic devices for applications in the complementary metal-oxide-semiconductor transistor (CMOS) industry. However, defects introduced by SAMM-doping will limit the performance of the devices. Previously, we have found that SAMM-doping can bring carbon impurities into the silicon substrate and these unwanted carbon impurities can deactivate phosphorus dopants by forming an interstitial carbon (C i )–substitutional phosphorus (C i –P s ) complex. Herein, to develop a defect-free SAMM-doping process, the generation and annihilation of C i -related defects are investigated by extending the thermal annealing time from 2 to 10 min using secondary ion mass spectrometry and deep-level transient spectroscopy. The results show that the concentration of C i -related carbon defects is lower after a longer time of thermal annealing, although a longer annealing time actually introduces a higher concentration of carbon impurities into Si. This observation indicates that interstitial carbon evolves into substitutional carbon (C s ) that is electrically inactive during the thermal annealing process. A defect-free SAMM-doping process may be developed by an appropriate post-annealing process.