340 nm‐band high‐power InAlGaN quantum well ultraviolet light‐emitting diode using p‐type InAlGaN layers

Abstract

In order to achieve high‐efficiency ultraviolet (UV) light‐emitting diodes (LEDs), p‐type layers with sufficient hole concentration is quite important to suppress the electron overflow. We introduced Mg‐doped InAlGaN for p‐type layers of the UV‐LEDs for the purpose of obtaining higher hole concentration, and achieved high power CW operations of the UV‐LEDs. 340 nm‐band InAlGaN‐based multi‐quantum‐well (MQWs) UV‐LEDs with Mg‐doped InAlGaN electron‐blocking layer (EBL) and Mg‐doped InAlGaN layers were grown on sapphire substrates by metal‐organic chemical vapor deposition (MOCVD). The output power of UV‐LED with p‐InAlGaN layers was approximately 4.7 times larger than that with p‐AlGaN layers. Maximum output power and the external quantum efficiency (EQE) of the LED with p‐InAlGaN layers were 8.4 mW and 0.9%, respectively, at emission wavelength of 346 nm under room temperature (RT) CW operation. From these results, p‐InAlGaN is shown to be useful for the realization of high‐efficiency UV‐LEDs. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Recent progress of 220-280 nm-band AlGaN based deep-UV LEDs

“…We have achieved a high internal quantum efficiency (IQE) of 47% for 338 nm quaternary InAlGaN QWs and 352 nm 7.4 mW DC current operation of an InAlGaN QW UV LED on GaN substrate [13]. We also achieved 346 nm 8.4 mW CW power quaternary InAlGaN LED with p-type InAlGaN layers [14,15]. Recently we developed low threading dislocation density (TDD) AlN template on sapphire [16], and achieved efficient AlGaN-QW DUV-LEDs with emission wavelengths at 222-273 nm [17].…”

“…We also obtained the maximum output power of 0.014 mW and EQE of 0.003% for 222 nm AlGaN LED, under RT pulsed operation. Quaternary InAlGaN alloy is attracting much attention as candidate material for realizing DUV-LEDs, since efficient UV emission as well as higher hole concentration can be obtained [1,14,15], due to In-incorporation effects. In order to realize high-efficiency DUV-LEDs, it is necessary to achieve high IQE of QW emission.…”

Design and Growth of Deep UV-Range Single Crystalline ZnMgAlO Thin Films Lattice-Matched to ZnO

“…In fact, similar problems also exist in the case of the nitride semiconductors, which are the most intensively studied materials for UV optoelectronics. During the growth of AlGaN layers with high AlN fraction on GaN substrates, tensile stress accumulates and cracks are often generated to relax the stress, due to the lattice mismatch between the layers. , Furthermore, AlGaN is especially sensitive to the dislocations and it is difficult to fabricate efficient AlGaN UV devices with wavelength lower than ∼360 nm ( E g ∼3.4 eV). It is well-known that a high density of misfit dislocations exists within the AlGaN/GaN layers, which act as the nonradiative recombination center. , …”

Aluminum nitride nanowire light emitting diodes: Breaking the fundamental bottleneck of deep ultraviolet light sources

“…Aluminum gallium nitride (AlGaN) has attracted significant attention for deep ultraviolet (DUV) light emitting diodes (LEDs) and laser diodes (LDs) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 , and is positioned to replace conventional mercury-based light sources for water purification, sterilization, and bio-chemical detection. To date, however, the performance of planar AlGaN DUV devices has been fundamentally limited by the prohibitively large dislocation density and the extremely inefficient p-type doing, due to the structural and electrical properties of the end compound – AlN.…”