S. Hagedorn^a, S. Walde^a, A. Mogilatenko^a, M. Weyers^a, L. Cancellara^b, M. Albrecht^b, D. Jaeger^c

Published in:

J. Cryst. Growth, vol. 512, pp. 142-146 (2019).

Abstract:

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.

Keywords:

A1. Substrates; A1. Crystal morphology; A3. Physical vapor deposition processes; B1. Nitrides; B1. Sapphire

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