MIJ-NSR Vol. 1, Art. 33, J. L. Rouviere et al.

Correlation between surface morphologies and crystallographic structures of GaN layers grown by MOCVD on sapphire

This article was received on Thursday, June 20, 1996 and accepted on Tuesday, November 5, 1996.

Abstract

GaN layers deposited by MOCVD on sapphire have been characterized by Transmission Electron Microscopy (TEM). Two substrate orientations were used, (0 0 0 1) and(2

0).We determine the crystallographic structures (defect content and layer polarity) of three different types of GaN layers with different surface morphologies. Convergent Beam Electron Diffraction studies were particularly important to determine the polarity of the GaN layers. We find that polarity and surface diffusion are the factors that control the different growth modes. Unipolarity is obtained thanks to the annealing of the low temperature buffer layer or/and thanks to the nitridation of the sapphire substrate.

Hexagonal pyramids and flat tops are formed when the material has a dominant N-polarity. The pyramids contain many tiny hexagonal columnar Inversion Domains (IDs). These pyramids are formed when the tiny Ga-polar IDs grow faster than the surrounding N-polar matrix. Flat GaN layers are unipolar, with a Ga polarity. Rough grainy layers which are unipolar (Ga-polarity) are obtained when surface diffusion is not high enough.

Outline

Introduction

Experimental details

Experimental results

GaN layers with hexagonal pyramids and flat tops

Flat GaN films

Rough grainy surface GaN films

Conclusion

Acknowledgments

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Cite this article as: MRS Internet J. Nitride Semicond. Res. 1, 33(1996).

last updated Tuesday, February 10, 2004 5:20:36 PM.