Vapor phase epitaxy of AlGaN base layers on sapphire substrates for nitride-based UV-light emitters

Abstract

UV transparent lattice matched substrates, e.g., AlN and AlGaN, with low dislocation densities are required for the epitaxial growth of UV-LED structures. In the absence of inexpensive high-quality UV transparent AlN bulk substrates, the heteroepitaxial growth of AlN base layers on relatively cheap and readily available sapphire substrates is the commonly used approach for most UV-B and UV-C LEDs. This chapter provides an insight into growth, strain management, and dislocation reduction techniques in metalorganic vapor phase epitaxy (MOVPE) of AlN and hydride vapor phase epitaxy (HVPE) of AlGaN layers. For both MOVPE and HVPE epitaxial lateral overgrowth of patterned substrate surfaces is an important technique to enhance the thickness of crack-free layers. This opens the route to UV-LEDs with improved performance.