Effect of template morphology on the efficiency of InGaN∕GaN quantum wells and light-emitting diodes grown by molecular-beam epitaxy

Abstract

The pronounced enhancement of indium incorporation efficiency for InGaN∕GaN quantum wells due to the rough, faceted surface of the GaN template grown in situ by ammonia-molecular-beam epitaxy is reported. The InGaN∕GaN quantum wells are grown by plasma-assisted molecular-beam epitaxy. Unlike the smooth (0002) surface of GaN template layers grown by metalorganic chemical vapor deposition, the surface of the template layers grown by ammonia-molecular-beam epitaxy is defined by {10-1m} pyramidal facets causing significant surface roughness. The drastically enhanced indium incorporation rate associated with the rough templates allows the InGaN∕GaN quantum wells to be grown at higher temperatures as it compensates for the increased thermal decomposition. High luminescence efficiency is achieved as a result. Using such efficient InGaN∕GaN quantum wells, light-emitting diodes have been grown entirely by molecular-beam epitaxy on sapphire substrates, demonstrating output power of 0.22mW for 20mA injection current.