Remarkable improvement in output power for an InAlGaN based ultraviolet LED by improving the crystalline quality of AlN/AlGaN templates

Abstract

The use of quaternary InAlGaN is very attractive for the realization of commercially‐available low‐cost and high‐power ultraviolet light‐emitting diodes (UV‐LEDs), because highly‐efficient UV emission can be obtained from this material due to In‐segregation effects. We achieved remarkable improvements in output power from 340 nm‐band quaternary InAlGaN‐based UV‐LEDs and demonstrated high UV‐output power by using high‐quality AlN buffer templates on sapphire substrates. Threading dislocation densities (TDDs) for screw and edge‐type dislocations were 1×108cm–2 and 1×109cm–2, as observed from cross‐sectional transmission electron microscope (TEM) images. The output power of a 340 nm‐band UV‐LED was increased by approximately 7 times by reducing the full‐width‐at‐half‐maximum (FWHM) of the (10‐12) X‐ray ω‐scan rocking curve (XRC) from around 800 arcsec to 510 arcsec. As a result, we achieved a maximum output power of 7.1 mW under room‐temperature (RT) and continuous‐wave (CW) operation. From these results, we confirmed that the crystalline quality of AlN/AlGaN templates strongly affects the output power of UV‐LEDs. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Realization of 270 nm band AlGaN based UV‐LEDs on large area AlN templates with high crystalline quality

“…In the case of the (10-12) XRC, the FWHM increased from 510 arcsec to 580 arcsec away from the center of the wafer. In the cases where AlGaN/AlGaN and InAlGaN/InAlGaN MQWs were used for UV region, the PL intensities were dramatically increased by improving the FWHMs to 500 arcsec [2,14]. On the other hand, the FWHM of the (0002) XRC was slightly increased from 170 arcsec to 190 arcsec.…”

Numerical simulation of UV LEDs with GaN and BGaN single quantum well

“…In this context recently various studies have been realized such as the using of the low-temperature barriers to improve strain relaxation and high performance GaN based LEDs where the authors success to increase the strain-relaxed mechanism of low-temperature barriers and address this problem [8][9][10][11][12] . Maximum output power and external quantum efficiency were obtained by employing 222-282 nm AlGaN and InAlGaN-based deep UV LEDs fabricated on low threading dislocation density AlN template [13] , and different growth methods were proposed to obtain AlGaN/AlN templates to obtain low threading dislocation density (TDD) [12-14, ] .…”