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Effect of Fermi Level Pinning at the Surface During OMVPE Growth

Published online by Cambridge University Press:  26 February 2011

R. M. Cohen ,
C. Y. Chen ,
W. M. Li ,
D. S. Simons  and
P. H. Chi
R. M. Cohen
Affiliation:
Dept. of Materials Science and Engineering, Univ. of Utah, Salt Lake City, UT 84112
C. Y. Chen
Affiliation:
Dept. of Materials Science and Engineering, Univ. of Utah, Salt Lake City, UT 84112
W. M. Li
Affiliation:
Dept. of Materials Science and Engineering, Univ. of Utah, Salt Lake City, UT 84112
D. S. Simons
Affiliation:
NIST Chemical Science and Technology Laboratory, Gaithersburg, MD 20899
P. H. Chi
Affiliation:
NIST Chemical Science and Technology Laboratory, Gaithersburg, MD 20899
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Abstract

During organometallic vapor phase epitaxy of GaAs, the Fermi energy is found to be pinned ≈200 meV below the intrinsic Fermi energy on a (lOO)-oriented surface. This was determined by making the first comparison of Zn concentration, Nzn. obtained from growth with that obtained at equilibrium, all under the same nominal ambient conditions. Donor solubility has been found to be virtually unchanged during growth of n- or p-type GaAs, and this is strong evidence that the Fermi level remains pinned at essentially the same energy during growth of n- or p-type GaAs. Consistent with Fermi level pinning, we find (1) the NZn is supersaturated in the epilayer for the ambient growth conditions used, (2) a large excess concentration of positively charged Ga interstitials can be grown into n-type GaAs and which diffuses into nearby p-type layers, causing (3) the Zn diffusivity, DZn ∼10−13 cm2/s, out of buried npn layers to be essentially independent of the ambient conditions. Annealing of a heavily Zn-doped layer at the surface can lead to 10−16<DZn<10−13 cm2/s at T=800°C simply by varying the Zn partial pressure over its commonly used range. Use of In-doped spikes in n- and p-type GaAs suggest that interstitial point defects have a strong effect on the group III diffusion.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 378: Symposium B – Defect and Impurity-Engineered Semiconductors and Devices , 1995 , 875
Copyright
Copyright © Materials Research Society 1995

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References

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