Band offsets and Fermi level pinning are extremely important issues for metal-oxide-semiconductor (MOS) device structures. In particular, there is increased interest in III-V semiconductor/ high-κ dielectric materials as a future replacement to conventional Si-based complementary MOS technology. In this work, we present band alignment measurements of Al2O3 grown by atomic layer deposition (ALD) on n-GaAs and p-GaAs by combined x-ray (XPS) and ultraviolet (UPS) photoemission spectroscopy. Influence of processing conditions (pre-growth, during growth, and post-growth) and substrate orientation on the Fermi level pinning is discussed. Pinning effects are more problematic on n-GaAs than p-GaAs, due in part to the fact that n-GaAs more readily forms As oxides that have been attributed to high interface gap state densities that cause pinning. Interestingly, at the first few layers of ALD grown at “self cleaning” conditions,[1, 2] native oxides on the GaAs for both n-type and p-type are significantly reduced, but the interfaces on n-GaAs are still strongly pinned. Best results for un-pinning of the Fermi levels between n-GaAs and p-GaAs is observed for Al2O3 / GaAs(111) samples having clean interfaces, grown at condition, and post-deposition annealing at 600° C in forming gas.

  

1. M. M. Frank, G.D.W., D. Starodub, T. Gustafsson, E. Garfunkel, Y. J. Chabal, J. Grazul, and D. A. Muller, Appl. Phys. Lett. 86, 152904 (2005).

2. H.D. Lee, T.F., L. Yu, D. Mastrogiovanni, A. Wan, T. Gustafsson, and E. Garfunkel, Appl. Phys. Letters (submitted), 2009.