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High‐Temperature Annealing of AlGaN
Author(s) -
Hagedorn Sylvia,
Khan Taimoor,
Netzel Carsten,
Hartmann Carsten,
Walde Sebastian,
Weyers Markus
Publication year - 2020
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.202000473
Subject(s) - annealing (glass) , materials science , alloy , transmittance , dislocation , ultraviolet , optoelectronics , analytical chemistry (journal) , composite material , chemistry , chromatography
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 Al 0.77 Ga 0.23 N 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 × 10 9 down to 2.6 × 10 9 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.