222-282 nm AlGaN and InAlGaN-based deep-UV LEDs fabricated on high-quality AlN on sapphire

We demonstrate 222-282 nm AlGaN and InAlGaN-based deep ultraviolet (DUV) light-emitting diodes (LEDs) fabricated on low threading dislocation density (TDD) AlN template. Low TDD AlN templates were realized by using ammonia (NH3) pulse-flow multilayer (ML) growth technique. The edge- and screw-type dislocation densities of AlN layer were reduced to 7.5 x 10(8) and 3.8 x 10(7), respectively. Single-peaked electroluminescence (EL) were obtained for 222-273 nm AlGaN multi quantum well (MQW) DUV-LEDs. We obtained the maximum output power of 1.1 mW and 4.0 mW for the AlGaN-QW LEDs with wavelengths of 241 nm, 256 nm, respectively, under room temperature (RT) CW operations. The maximum output power of 227 nm and 222 nm AlGaN-QW were 0.15 mW and 0.014 mW, respectively, under RT pulsed operation. The maximum external quantum efficiency (EQE) of the 227 nm and 250 nm AlGaN LEDs were 0.2% and 0.43%, respectively. We also fabricated 280 nm band quaternary InAlGaN-MQW DUV-LEDs with n-type and p-type InAlGaN layers on ML-AlN templates. We demonstrated extremely high internal quantum efficiency (IQE) of 284 nm InAlGaN-QW emission, which was confirmed by the fact that the ratio of the integrated intensity of the RT-PL against the 77 K-PL was 86%. The maximum output power and EQE of the 282 mn InAlGaN LED were 10.6 mW and 1.2%, respectively, under RT CW operation. (C) 2009 WILEY-VCH Veriag GmbH & Co. KGaA, Weinheim