Improved performance of 325-nm emission AlGaN ultraviolet light-emitting diodes

Abstract

We report on AlGaN multiple-quantum-well light-emitting diodes over sapphire with peak emission at 325 nm. A pulsed-atomic-layer-epitaxy growth process was used to improve the material quality of the AlN buffer and the AlN/AlGaN strain-relief layers for reducing the nonradiative recombination. In addition, a modified device epilayer structure was used to improve the carrier confinement and the hole injection. A 40% improvement of external quantum efficiency is obtained, resulting in record high optical powers of 10.2 mW at a pulsed pump current of 1 A.

Direct evidence of compositional pulling effect in Al Ga1−N epilayers

“…Group-III nitride semiconductors (AlGaN) can be developed for application in ultra-violet (UV) light emitters, UV photodetectors, white light emitters [1,2], and high-power electronics [3], because of its wide band gap distribution from 3.42 to 6.2 eV. The key issues for the growth of high-quality AlGaN epitaxial layers are crack formation and poor crystallization [4].…”

Status of Growth of Group III-Nitride Heterostructures for Deep Ultraviolet Light-Emitting Diodes

“…Chitnis et al [98] also demonstrated improved performance in DUV LEDs with AlN/AlGaN superlattice buffer layer. By using the pulsed atomic layer epitaxy (PALE) approach discussed in Section 6, and an AlN/Al 0.85 Ga 0.15 N superlattice strain-relief buffer, output power levels of 10.2 mW at 1 A pulsed current and 1 mW at 100 mA CW current were achieved in LEDs emitting at 325 nm and grown on sapphire substrates.…”

Efficient silicon based light emitters

“…Gd 3C has a luminescent transition at a wavelength of 316 nm and therefore needs a very-large band-gap host material [34]. Presently, deep UV LEDs are mostly based on AlGaN [35][36][37], whereas for the green LEDs InGaN [38] or AlGaInP [39] are employed. The substitution of those materials by Si MOS structures would be highly desirable for low-cost and integrated applications.…”