Status and Prospects of AlN Templates on Sapphire for Ultraviolet Light‐Emitting Diodes

Herein, the scope is to provide an overview on the current status of AlN/sapphire templates for ultraviolet B (UVB) and ultraviolet C (UVC) light‐emitting diodes (LEDs) with focus on the work done previously. Furthermore, approaches to improve the properties of such AlN/sapphire templates by the combination of high‐temperature annealing (HTA) and patterned AlN/sapphire interfaces are discussed. While the beneficial effect of HTA is demonstrated for UVC LEDs, the growth of relaxed AlGaN buffer layers on HTA AlN is a challenge. To achieve relaxed AlGaN with a low dislocation density, the applicability of HTA for AlGaN is investigated. AlGaN‐based light‐emitting diodes with emission in the ultraviolet B (UVB) and ultraviolet C (UVC) spectral range still suffer from a lack of high‐quality substrate material. Herein, an overview of possible approaches to meet this challenge focusing on AlN grown by metal–organic chemical vapor deposition on c‐plane‐oriented sapphire substrates is provided.