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Enhanced Tunneling through sub 30 Angstroms Thick Gallium Nitride Cap Layers on Silicon Carbide for Low Contact Resistance

Published online by Cambridge University Press:  01 February 2011

Choudhury Jayant Praharaj*
Affiliation:
cjp1414@yahoo.com, Unaffiliated, Unaffiliated, 1901 Halford Avenue, Apt 74, Santa Clara, CA, 95051, United States
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Abstract

We present numerical calculations of tunneling through ultra thin wurtzite Gallium Nitride cap layers on p-doped wurtzite silicon carbide . We demonstrate the predominance of tunneling of the split-off holes to the total carrier flux, with the contribution of the heavy and the light holes damped by the large potential barrier. We calculate the contributions of spontaneous and piezoelectric polarizations to the tunneling profile seen by the holes. Two orders of magnitude enhancement is seen in the transmission probabilities for a 10 angstroms thick Gallium Nitride cap layer for holes very close to the valence band edge, compared to a barrier without any gallium nitride cap. The contact resistances are also calculated for the Gallium Nitride tunneling caps and more than two orders of magnitude lowering is seen with the ultra-thin caps. Larger cap widths induce hole accumulation layers, but the advantages of hole accumulation are offset by the higher effective tunneling width. Our calculations are relevant to nanostructures and nanodevices involving heterojunctions between gallium nitride and silicon carbide and provide the basis for low contact resistances with as-deposited metals. While our calculations focus on the regime of very high barriers to the metal of the order of 1.5 - 2 electron volts, where the method of ultra-thin caps is most useful, similar conclusions also hold for lower barrier heights.

Type
Research Article
Copyright
Copyright © Materials Research Society 2007

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References

1. Bernardini, F and Fiorentini, V, Nonlinear macroscopic polarization in III-V nitride alloys, Physical Review B (Condensed Matter and Materials Physics), 2001, vol 64, no.8 Google Scholar
2. Gessman, T et al. Ohmic contact technology in III nitrides using polarization effects of cap layers, Journal of Applied Physics, 2002, Vol 92, No 7, 37403744 Google Scholar
3. Ambacher, O et al. . Pyrolectric properties of Al(In)GaN/GaN hetero- and quantum well structures, Journal of Physics: Condensed Matter, 2002, vol 14, no 13, pp 339434.Google Scholar
4. Qteish, A, Heine, V and Needs, R, Polarization, band lineups and stability of SiC polytypes, Physical Review B, Vol 45, no 12, 1992, pp 6534 Google Scholar
5. Jackson, J.D, Classical Electrodynamics, John Wiley and Sons, 1999 Google Scholar
6. Sherwin M., E. and Drummond T., J, Predicted elastic constants and critical layer thicknesses for cubic phase AlN, GaN and InN on β-SiC, Journal of Applied Physics, Vol 69, no 12, 1991 Google Scholar
7. Lin, et al, Enhancement of Schottky barrier height on p-type GaN by (NH4)2Sx teatment Journal of Applied Physics, Vol 99. No 5, 2006 Google Scholar
8. Hu, J et al. Highly sensitive visible-blind extreme ultraviolet Ni/4H-SiC Schottky photodiodes with large detection area, Optics Letters, Vol 31, no 11, 2006 Google Scholar
9. Tumakha, S et al. . Defect-driven inhomogenities in Ni/4H-SiC Schottky barriers, Applied Physics Letters, 2005, Vol 87, no 24, 2005 Google Scholar
10. Chen, C.H et al. Valence band discontinuity at the GaN/sic(0001) heterojunction studied in situ by synchrotron-radiation photoelectron spectroscopy, Journal of Electron Spectroscopy and Related Phenomena, v 144-147, June 2005, pp 425–8Google Scholar
11. Lambrecht W.R., L et al. Eletcronic Band Structure of SiC polytypes: A Discussion of Theory and Experiment, Physica Status Solidi (b), Vol 202, no 5, 1997 Google Scholar
12. Kim, K et al. Effective masses and valence-band splittings in GaN and AlN, Physical Review B, Vol 56, no 12, 1997, pp 7363 Google Scholar