Heteroepitaxial three dimensional (3D) and two dimensional (2D) growth mode of nitride layers on sapphire substrates are discussed. It is shown that the 3D or 2D growth mode of AlGaN layers depends predominantly on the growth conditions of the underneath grown low temperature (LT) nucleation layer.

Commonly described in literature 3D growth mode is obtained on LT GaN or AlN nucleation layer grown relatively fast. Successive growth of secondary layer at high temperature begins from separated sites, where individual 3D crystallites are formed. Threading dislocations present in crystallites are bending on their facets, which reduces the quantity of dislocations. However, from the other hand, slight crystallographic misorientations between crystallites leads to creation of new dislocations which are generated during coalescence of the crystallites. As result edge and mix dislocations appearing are at similar density of about 10⁹ cm^-2.

Modification of growth conditions of LT AlN nucleation layer, especially reduction of their growth rate leads to drastic changes in properties of the layer. Successive growth of secondary AlGaN layer at high temperature starts evenly on whole surface retaining atomic flatness. Thus, the growth at high temperature occurs only at 2D mode. Therefore, it is possible to grow a very thin AlGaN layers directly on top of LT AlN nucleation layer. Such layers contain large number (10¹⁰ cm^-2) of edge dislocations, and relatively small number (less then 10⁸ cm^-2) of mix dislocations.

It is also shown, that decisive factors which determine the growth mode of AlN nucleation layer is a growth of the first few atomic layers on substrate surface. The slow growth of this few first atomic layers decide about the 2D growth mode, and the fast one about the 3D one.

• Legal notice:
  

  Copyright (c) Pielaszek Research, all rights reserved.
  The above materials, including auxiliary resources, are subject to Publisher's copyright and the Author(s) intellectual rights. Without limiting Author(s) rights under respective Copyright Transfer Agreement, no part of the above documents may be reproduced without the express written permission of Pielaszek Research, the Publisher. Express permission from the Author(s) is required to use the above materials for academic purposes, such as lectures or scientific presentations.
  In every case, proper references including Author(s) name(s) and URL of this webpage: https://science24.com/paper/9943 must be provided.

1. Influence of  SiC substrate orientation on epitaxial graphene quality studied by Raman spectroscopy
2. Pinned and unpinned epitaxial and sublimated graphene on SiC
3. Graphene epitaxy by chemical vapor deposition on SiC.
4. Raman spectroscopy of single and multilayer graphene on SiC substrates
5. Spontaneous Superlattice Formation in MOCVD Growth of AlGaN
6. Recombination Dynamics in GaN/AlGaN Low Dimensional Structures Obtained by SiH₄ Treatment
7. Electroreflectance and photoreflectance studies of AlGaN/GaN heterostructure with a QW placed inside AlGaN layer
8. Optical Detection of 2DEG in GaN/AlGaN Structures - High Magnetic Field Studies
9. Light induced contrast in Kelvin Force Microscopy of GaN epilayers