Ultraviolet light-emitting diodes based on group three nitrides

Khan, Asif; Balakrishnan, Kalpana; Katona, Tom

doi:10.1038/nphoton.2007.293

Cited by 945 publications

(581 citation statements)

References 81 publications

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“…AlGaN based light emitting diodes (LEDs) are the main source for solid state UV emitters mainly because of the wide range of direct band gaps spanning the UVA, UVB, and UVC range [2]- [6].…”

Section: Introductionmentioning

confidence: 99%

Tunnel junction enhanced nanowire ultraviolet light emitting diodes

Sarwar

May

Deitz

et al. 2015

Applied Physics Letters

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Polarization engineered interband tunnel junctions (TJs) are integrated in nanowire ultraviolet (UV) light emitting diodes (LEDs). A ∼6 V reduction in turn-on voltage is achieved by the integration of tunnel junction at the base of polarization doped nanowire UV LEDs. Moreover, efficient hole injection into the nanowire LEDs leads to suppressed efficiency droop in TJ integrated nanowire LEDs. The combination of both reduced bias voltage and increased hole injection increases the wall plug efficiency in these devices. More than 100 μW of UV emission at ∼310 nm is measured with external quantum efficiency in the range of 4–6 m%. The realization of tunnel junction within the nanowire LEDs opens a pathway towards the monolithic integration of cascaded multi-junction nanowire LEDs on silicon.

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Section: Introductionmentioning

confidence: 99%

Tunnel junction enhanced nanowire ultraviolet light emitting diodes

Sarwar

May

Deitz

et al. 2015

Applied Physics Letters

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“…The smooth and roughened devices show similar electrical behavior, with a voltage drop of 5.15 V at 20 A/cm 2 (Fig. 3).…”

mentioning

confidence: 79%

“…As a solution, light is most efficiently extracted from the substrate side of the devices using flip chip bonding. [2][3][4][5][6][7] To reduce internal reflection, micro-structure patterning has to be done on the back side of the devices, and device encapsulation and packaging is necessary. Despite these techniques, the achieved light extraction efficiency is only 25% 8 , which is much lower than the visible LEDs (> 80%) 9 .…”

mentioning

confidence: 99%

Enhanced light extraction in tunnel junction-enabled top emitting UV LEDs

Zhang

Allerman

Krishnamoorthy

et al. 2016

Appl. Phys. Express

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Abstract:The efficiency of ultra violet LEDs is critically limited by the absorption losses in ptype and metal layers. In this work, surface roughening based light extraction structures are combined with tunneling-based top-contacts to realize highly efficient top-side light extraction efficiency in UV LEDs. Surface roughening of the top n-type AlGaN contact layer is demonstrated using self-assembled Ni nano-clusters as etch mask. The top surface roughened LEDs were found to enhance external quantum efficiency by over 40% for UV LEDs with a peak emission wavelength of 326 nm. The method described here can enable highly efficient UV LEDs without the need for complex manufacturing methods such as flip chip bonding.III-Nitride ultra-violet light emitting diodes (UV LEDs) have attracted great research interest due to the large range of applications including water purification, air disinfection, curing, and phototherapy. 1 In the past decade, because of the improvement in substrate quality and optimization of both the active region design and fabrication, LED efficiency and power have a)

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“…The advances in the heteroepitaxial growth have successfully demonstrated deep-UV light-emitting diodes (LEDs) and photo-pumped AlGaN multiple-quantum-well lasers. [3][4][5][6][7] However, the radiative emission efficiencies of deep-UV light emitters are still low, prompting for further reduction of dislocations that act as non-radiative recombination centers. [3][4][5][6] The heteroepitaxial growth between AlN and sapphire substrate induces several types of dislocations, driven by their lattice mismatch and difference in crystal structure.…”

mentioning

confidence: 99%

Influence of surface structure of (0001) sapphire substrate on the elimination of small-angle grain boundary in AlN epilayer

2015

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AlN epilayers were grown on (0001) sapphire substrates by metal-organic vapor phase epitaxy, and the influence of the substrate’s surface structure on the formation of in-plane rotation domain is studied. The surface structure is found to change with increasing temperature under H2 ambient. The ML steps of sapphire substrate formed during high-temperature (HT) thermal cleaning is found to cause the formation of small-angle grain boundary (SAGB). To suppress the formation of such structure, the use of LT-AlN BL technique was demonstrated, thereby eliminating the SAGB. The BL growth temperature (Tg) is also found to affect the surface morphology and structural quality of AlN epilayer. The optical emission property by cathodoluminescence (CL) measurement showed higher emission intensity from AlN without SAGB. The LT-AlN BL is a promising technique for eliminating the SAGB.

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Ultraviolet light-emitting diodes based on group three nitrides

Cited by 945 publications

References 81 publications

Tunnel junction enhanced nanowire ultraviolet light emitting diodes

Tunnel junction enhanced nanowire ultraviolet light emitting diodes

Enhanced light extraction in tunnel junction-enabled top emitting UV LEDs

Influence of surface structure of (0001) sapphire substrate on the elimination of small-angle grain boundary in AlN epilayer

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