Progress in Performance of AlGaN‐Based Ultraviolet Light Emitting Diodes

Abstract

AlGaN‐based ultraviolet light‐emitting diodes (UV‐LEDs) have the advantages of mercury (Hg) pollution free, small size, high efficiency, and so on, and are widely used in military, medical, and industrial fields, which are considered to be the most promising alternative to the traditional Hg lamps. Great efforts are made over the past few decades to improve the device performance, thereby meeting the commercial production and application requirements of UV‐LEDs, which is always accompanied by a series of interesting physical topics. In this review, the recent research progress in performance of AlGaN‐based UV‐LEDs is summarized from the perspectives of electrical injection, electro‐optical conversion, and light extraction, which are responsible for the operation of devices. The detailed discussions include the major challenges, the corresponding technological breakthroughs, and also the outlook of material growth, energy band modulation, as well as device fabrication involved in UV‐LEDs, which are expected to be helpful for the thorough comprehension of device physics and further development of AlGaN‐based UV‐LEDs.

Effect of stress control by growth adjustment on the edge thread dislocation density of AlN grown on the sapphire

“…The sample A3 was subjected to the smallest tensile stress during growth, less than 0.1 Gpa, and the corresponding edge TDD was as low as 6.31 × 10 7 cm −2 , the TDD was 1.2 × 10 8 cm −2 . This is a pretty good value of epitaxial AlN grown on flat sapphire substrates reported before [3,[39][40][41]. To the best of our knowledge, the previous lowest TDD result for MOCVD direct epitaxy of AlN on a flat sapphire substrate was 1.5 × 10 8 cm −2 .…”