Abstract
High-temperature annealing of sputtered AlN (Sp-AlN) using a face-to-face configuration is a novel technique that has attracted considerable attention because it can reduce the threading dislocation density of Sp-AlN to 107 cm−2. However, drawbacks such as cracking, residual stress, and wafer curvature remain because of a high annealing temperature of 1700 °C. We previously developed a thermal strain analysis model that uses an elastic multilayer system to describe the elastic behavior of Sp-AlN on sapphire under high-temperature annealing. In this study, we expand this model to consider in-plane anisotropy. By performing thermal strain analysis of the curvature, strain, stress, and strain energy of c-plane AlN grown on c- and a-plane sapphire, our calculation successfully approximates the experimental results, even for an in-plane anisotropic structure. The proposed model is, therefore, useful for quantitative evaluation of the residual strain and can contribute to strain engineering of AlGaN-based deep-ultraviolet light-emitting diodes.
Highlights
High-temperature annealing of sputtered AlN (Sp-AlN) using a face-to-face configuration (FFA) is a novel technology that has attracted considerable attention because of its ability to reduce the threading dislocation density (TDD) of Sp-AlN
We previously developed a thermal strain analysis model that uses an elastic multilayer system to describe the elastic behavior of Sp-AlN on sapphire under high-temperature annealing
We performed thermal strain analysis of FFA Sp-AlN grown on c- and a-plane sapphire (a-Sap) by considering in-plane anisotropy when modeling the relevant elastic multilayer system
Summary
High-temperature annealing of sputtered AlN (Sp-AlN) using a face-to-face configuration (FFA) is a novel technology that has attracted considerable attention because of its ability to reduce the threading dislocation density (TDD) of Sp-AlN. This characteristic aids the production of AlGaN-based deep-ultraviolet lightemitting diodes (DUV LEDs) on sapphire substrates.. In addition to conventional c-plane sapphire (cSap) substrates, this method has been successfully applied to heteroepitaxial growth on a-plane sapphire (a-Sap), SiC, diamond, and nanopatterned sapphire substrates.9–13 Drawbacks such as residual stress, wafer bowing, and film cracking appear due to coefficient of thermal expansion (CTE) mismatches between AlN and the substrate.
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