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

Abstract

AbstractWe 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 × 108 and 3.8 × 107, 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 nm InAlGaN LED were 10.6 mW and 1.2%, respectively, under RT CW operation. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)