Guy Cohen1 Marinus Hopstaken1 Michael Saccomanno1 William Spratt1 Paul Solomon1 Christian Lavoie1 Renee Mo1 Sang-Moon Lee2 Jungtaek Kim2 Woo-Bin Song2 Doron Cohen Elias3

1, IBM T.J. Watson Research Center, Yorktown Heights, New York, United States
2, Samsung Electronics Co., Gyeonggi-do, , Korea (the Republic of)
3, Soreq Nuclear Research Center, Yavne, , Israel

We report the depletion of silicon dopants at the surface of epitaxially grown in-situ doped InAs layers. The lower concentration of Si doping at the surface is technologically significant as it leads to increase in contact resistance.
The depletion of Si was observed in metal-organic chemical vapor deposition (MOCVD) grown Si doped InAs layers as well as in InAs layers grown by atomic layer epitaxy (ALE). In situ doping was employed to make InAs layers with [Si] concentration from 2E18 to 8E19 cm-3.
Secondary ion mass spectrometry (SIMS) was used to study the Si profile in the Si doped InAs layers. It was found that the silicon depletion was larger for higher doping levels of Si in the bulk of the InAs layer. The Si depletion extends to about 5 nm from the InAs surface. We have employed Ultra-Low Energy (ULE-) SIMS (250 – 400 eV Cs+ ion impact energy) to demonstrate that the Si depletion width extends well beyond the InAs native oxide thickness and SIMS surface transient depth.
The top 8 nm of the InAs layers were controllably etched by self-limited digital etching to remove the Si depleted region. The SIMS Si profile of etched InAs does not exhibit Si depletion, thus suggesting that depletion of Si atoms near the surface takes place during the layer growth.
Co-doping the InAs layer with silicon and zinc (a p-type dopant) did not change the Si depletion profile near the surface. This suggests that the depletion of the silicon atoms near the surface is not a result of an electrical field induced by surface pinning [1].

1. E. F. Schubert, Doping in III-V Semiconductors, Cambridge university press, 1993.