Properties of GaN epitaxial layers grown on 6H-SiC(0001) by plasma-assisted molecular beam epitaxy |
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| Authors: | C D Lee V Ramachandran A Sagar R M Feenstra D W Greve W L Sarney L Salamanca-Riba D C Look Song Bai W J Choyke R P Devaty |
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| Affiliation: | (1) Department of Physics, Carnegie Mellon University, 15213 Pittsburgh, Pennsylvania;(2) Department of Electrical and Computer Engineering, Carnegie Mellon University, 15213 Pittsburgh, PA;(3) Materials and Nuclear Engineering Department, University of Maryland, 20742-2115 College Park, MD;(4) Wright State University of Air Force Research Laboratory, 45435 Dayton, Ohio;(5) Department of Physics and Astronomy, University of Pittsburgh, 15260 Pittsburgh, Pennsylvania;(6) Present address: IBM Microelectronics, 05452 Essex Junction, Vermont |
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| Abstract: | The structural, electrical, and optical properties of GaN grown on 6H-SiC(0001) substrates by molecular beam epitaxy are studied.
Suitable substrate preparation and growth conditions are found to greatly improve the structural quality of the films. Threading
dislocation densities of about 3×109 cm−2 for edge dislocations and <1×106 cm−2 for screw dislocations are achieved in GaN films of 0.8 μm thickness. Mechanisms of dislocation generation and annihilation
are discussed. Increasing the Ga to N flux ratio used during growth is found to improve the surface morphology. An unintentional
electron concentration in the films of about 5×1017 cm−3 is observed, and is attributed to excess Si in the films due to a Si-cleaning step used in the substrate preparation. Results
from optical characterization are correlated with the structural and electronic studies. |
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| Keywords: | GaN SiC molecular beam epitaxy dislocation density scanning tunneling microscopy |
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