Much of the best GaN material grown today is produced in cold-wall MOCVD reactors by running TMGa and NH₃ in a very high V-to-III gas-flow ratio,~10³ and up to 40000, since a high NH₃ partial pressure is necessary to alleviate nitrogen loss during the growth.
The aim of this work is to explore the growth of AlN, AlGaN and GaN on SiC substrates in a lower V-to-III gas-flow ratio range, which may have advantages in avoiding the excess ammonia supply, reduced adduct formation and less toxic exhaust while achieving layers of device quality material. The growth runs are performed in a hot-wall MOCVD system, which is a new approach to the MOCVD growth of III-nitrides, though for the growth of device quality SiC epitaxial layers the situation is different. Today, the hot-wall reactor design dominates the SiC CVD world market and it is proven to supply very good heating efficiency, temperature homogeneity and uniform characteristics of the layers.
In the present experiments, with nitrogen as a carrier, TMAl and TMGa are added to NH₃ at N-to-Al and N-to-Ga gas-flow ratio of ~50 and 250, respectively. The NH₃ flow is 50 ml/min and the precursors are delivered jointly.
High speed growth of epitaxial AlN and Al_0.2Ga_0.8N layers are achieved, 1.5 and 3 μm/h, respectively, at a growth temperature of 1200^oC. The data analysis of the IR spectroscopic ellipsometry response of a 380 nm thick AlN, 55 nm thick Al_0.2Ga_0.8N, and 580 nm thick GaN layer provides the following results: E₁(TO) phonon mode broadening values of 5cm^-1, 4.2cm^-1 and 4.6cm^-1, respectively. Small E₁(TO) broadening value indicates high compositional homogeneity and high crystal quality.
As a next step, we will show results from epitaxial growth under same growth conditions but using H₂ as a carrier gas. For example, relatively higher E₁(TO) broadening value, 5.7cm^-1, is measured for an AlN layer with similar thickness,~340 nm, grown however in 60 min when in H₂ ambient.
[ABS
[ABSTRACT TRUNCATED TO 2000 LETTERS]

• 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/1994 must be provided.