Ultraviolet light emitting diodes by ammonia molecular beam epitaxy on metamorphic (202¯1) AlGaN/GaN buffer layers

In this paper we demonstrate ultraviolet (UV) light emitting diodes (LEDs) grown on metamorphic AlGaN buffers on freestanding GaN (202¯1) substrates by ammonia assisted molecular beam epitaxy (MBE). Misfit and related threading dislocations were confined to the stress relaxed, compositionally graded buffer layers, and single quantum well devices emitting at 355, 310 and 274 nm were grown on top of the graded buffers. The devices showed excellent structural and electrical (I-V) characteristics.