AlGaN deep ultraviolet LEDs on bulk AlN substrates

We report the growth of sub‐300 nm ultraviolet light emitting diodes (UV LEDs) on bulk AlN substrates. Heteroepitaxial evolution study through interrupted growth experiments revealed that Al x Ga 1‐x N (x > 0.5) epilayers can be grown pseudomorphically with well‐defined step‐flow growth mode below a certain critical thickness. The build‐up of compressive strain energy eventually induces a morphological roughening followed by the admission of misfit dislocations. LEDs grown on bulk AlN substrates exhibit noticable improvement over those on sapphire in device impedance, efficiency and thermal characteristics under high‐level injection, pointing to a promising substrate platform for high performance III‐nitride ultraviolet optoelectronics. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)