A critical evaluation of Ag- A nd Ti-hyperdoped Si for Si-based infrared light detection

S. Q. Lim*, A. J. Akey, E. Napolitani, P. K. Chow, J. M. Warrender, J. S. Williams

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    15 Citations (Scopus)


    Following recent successful demonstrations of enhanced infrared absorption in Au-hyperdoped Si, there has been strong interest in fabricating other metal-hyperdoped Si systems as a highly attractive approach for Si-based infrared photodetection. In this work, we address the somewhat contentious issue in the literature as to whether it is possible, using ion implantation and nanosecond pulsed-laser melting, to achieve hyperdoping of Si with Ag and Ti at concentrations exceeding that required to form an intermediate impurity band within the Si bandgap (N IB ∼ 6 × 10 19 cm-3). A wide range of characterization techniques were used to investigate these material systems, especially the quality of liquid-phase epitaxy, impurity concentration distribution both in depth and laterally, and impurity lattice location. Our results indicate that the high concentrations of opto-electrically active Ag or Ti in monocrystalline Si required to form an impurity band are not achieved. In particular, the usual behavior during rapid solidification is for near-complete surface segregation of the impurity, or for it to be trapped within a highly defective subsurface layer due to filamentary breakdown. Although our measurements showed that the maximum concentration of impurities outside metal-rich filaments is comparable to N IB for both Ag and Ti, there is no preferential Ag or Ti lattice location after pulsed-laser melting anywhere in the material. Thus, the concentration of opto-electrically active Ag and Ti that can be homogeneously incorporated into Si is expected to be well below N IB, leaving Au as the only viable impurity to date for achieving the required level of hyperdoping in Si.

    Original languageEnglish
    Article number065701
    JournalJournal of Applied Physics
    Issue number6
    Publication statusPublished - 14 Feb 2021


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