Stabilization of sputtered AlN/sapphire templates during high temperature annealing
J. Cryst. Growth, vol. 512, pp. 142-146 (2019).
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In this work we investigated annealing of 350 nm and 450 nm thick sputtered (SP) AlN on sapphire in the temperature range from 1650 °C to 1730 °C. The most distinct decrease in the threading dislocation density (TDD), from initially 3×1010 cm-2 to 4×108 cm-2, was achieved for 450 nm AlN at an annealing temperature of 1680 °C. Unfortunately, for temperatures ≥1680 °C the reaction between AlN and sapphire partially disturbs the AlN layer by formation of polycrystalline AlON at the AlN/sapphire interface. In addition, we found epitaxially oriented (1 1 1) AlON on top of the AlN layers that hinders further epitaxial growth. This problem can be prevented by lower annealing temperatures (≥1680 °C) and thick SP AlN layers. The importance of an appropriate AlN sputtered layer thickness and of a precise temperature control during high temperature annealing are shown in this paper to ultimately achieve a balance between low TDD and suppression of excessive AlON formation.
a Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Str. 4, 12489 Berlin, Germany
b Leibniz Institute for Crystal Growth, Max-Born-Str. 2, 12489 Berlin, Germany
c Evatec AG, Hauptstr. 1a, 9477 Trübbach, Switzerland
A1. Substrates; A1. Crystal morphology; A3. Physical vapor deposition processes; B1. Nitrides; B1. Sapphire