High-Temperature Annealing of AlGaN
S. Hagedorna, T. Khana, C. Netzela, C. Hartmannb, S. Waldea, and M. Weyersa
Published in:
phys. stat. sol. (a), vol. 217, no. 23, pp. 2000473, doi:10.1002/pssa.202000473 (2020).
Abstract:
In the past few years, high-temperature annealing of AlN has become a proven method for providing AlN layers with low dislocation densities. Herein, the example of Al0.77Ga0.23N is used to investigate whether annealing can also improve the material quality of the ternary alloy. A detailed analysis of the influence of annealing temperature on structural and optical material properties is presented. It is found that with increasing annealing temperature, the threading dislocation density can be lowered from an initial value of 6.0×109 down to 2.6×109 cm-2. Ga depletion at the AlGaN surface and Ga diffusion into the AlN buffer layer are observed. After annealing, the defect luminescence between 3 and 4 eV is increased, accompanied by an increase in the oxygen concentration by about two orders of magnitude. Furthermore, due to annealing optical absorption at 325 nm (3.8 eV) occurs, which increases with increasing annealing temperature. It is assumed that the reason for this decrease in ultraviolet (UV) transmittance is the increasing number of vacancies caused by the removal of group-III and N atoms from the AlGaN lattice during annealing.
a Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Strasse 4, 12489 Berlin, Germany
b Application Science Department, Leibniz-Institut für Kristallzüchtung, Max-Born-Str. 2, 12489 Berlin, Germany
Keywords:
AlGaN, high-temperature annealing, metalorganic vapor phase epitaxy, substrate, ultraviolet light-emitting diodes
Copyright © 2020 The Authors. Published by WILEY-VCH GmbH.
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