Origin of defect luminescence in ultraviolet emitting AlGaN diode structures

Feneberg, Martin; Romero, M. F.; Goldhahn, R.; Wernicke, Tim; Reich, Christoph; Stellmach, Joachim; Mehnke, Frank; Knauer, A.; Weyers, M.; Kneissl, Michael

doi:10.1063/5.0047021

Cited by 6 publications

(8 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[72] Since the early days of quantum mechanics, variational approaches have been used for framing eigenvalues of complex problems using trial functions, with the following teaching relevant for us here: eigenenergies can be obtained with rather close values, although trial functions are dramatically (but reasonably) different. In [26], red ones for QWs, this work). Experimental results recorded on samples grown by MOCVD (blue body-centered spotted open diamonds) taken from ref.…”

Section: Anisotropy Of the Edge-emission Polarization-resolved Diagra...mentioning

confidence: 77%

See 1 more Smart Citation

The Influence of Alloy Disorder Effects on the Anisotropy of Emission Diagrams in (Al,Ga)N Quantum Wells Embedded into AlN Barriers

Ibanez,

Leroux,

Nikitskiy

et al. 2024

Physica Status Solidi (b)

View full text Add to dashboard Cite

The polarized photoluminescence emitted on the edge of a series of aluminum‐rich (Al,Ga)N‐AlN quantum wells (QWs) grown by molecular beam epitaxy on AlN templates deposited by metal organic chemical vapor deposition on c‐plane sapphire is measured. The contrast and the principal axis of the emission diagrams for 2 nm‐thick (Al,Ga)N QWs grown for aluminum compositions between 40% and 90% are studied. The light is emitted on the edge of the QWs at wavelengths going from 280 nm down to 209 nm. The emission diagram, a change from oblate to prolate with respect to the in‐plane orientation, for an aluminum composition is found to occur around 72%, that is, at an emission wavelength of about 235 nm. The orientations and shapes of the edge‐emission diagrams indicate that the fluctuations of the composition of the (Al,Ga)N confining layer are deep enough for producing intravalence band mixings. This property, that acts in concert with the built‐in strain and quantum‐confined Stark effect, contributes to the anisotropy of the light emission when the aluminum composition reaches 60–70%, that is, for an emission wavelength of 260–235 nm.

show abstract

Section: Anisotropy Of the Edge-emission Polarization-resolved Diagra...mentioning

confidence: 77%

“…Figure 6. DOP measured in Al x Ga 1Àx N QD and QW samples (bodycentered spotted open circles for QDs, ref [26],. red ones for QWs, this work).…”

mentioning

confidence: 99%

The Influence of Alloy Disorder Effects on the Anisotropy of Emission Diagrams in (Al,Ga)N Quantum Wells Embedded into AlN Barriers

Ibanez,

Leroux,

Nikitskiy

et al. 2024

Physica Status Solidi (b)

View full text Add to dashboard Cite

show abstract

“…The initial overgrowth and faceting step can clearly be seen to introduce a significant point defect population, resulting in multiple luminescence bands in the range of 360–470 nm. These defect bands are ascribed to cation vacancy complexes and are commonly seen in AlGaN alloys. − The lack of a band edge emission peak from this layer could be due to the close compositional match to the core combined with the increased defect population. Note that the reactor employed for these overgrowth stages had not been optimized for high-temperature growth, which could explain the high concentration of point defects.…”

Section: Assembly Of Algan Core–shell Structuresmentioning

confidence: 99%

Core–Shell Nanorods as Ultraviolet Light-Emitting Diodes

et al. 2023

Self Cite

View full text Add to dashboard Cite

Existing barriers to efficient deep ultraviolet (UV) light-emitting diodes (LEDs) may be reduced or overcome by moving away from conventional planar growth and toward three-dimensional nanostructuring. Nanorods have the potential for enhanced doping, reduced dislocation densities, improved light extraction efficiency, and quantum wells free from the quantum-confined Stark effect. Here, we demonstrate a hybrid top-down/bottom-up approach to creating highly uniform AlGaN core–shell nanorods on sapphire repeatable on wafer scales. Our GaN-free design avoids self-absorption of the quantum well emission while preserving electrical functionality. The effective junctions formed by doping of both the n-type cores and p-type caps were studied using nanoprobing experiments, where we find low turn-on voltages, strongly rectifying behaviors and significant electron-beam-induced currents. Time-resolved cathodoluminescence measurements find short carrier liftetimes consistent with reduced polarization fields. Our results show nanostructuring to be a promising route to deep-UV-emitting LEDs, achievable using commercially compatible methods.

show abstract

“…The reported maximum light output power (LOP) of 20 × 20 mil 2 UV-B chips at 304 nm was 57.2 mW under an operating current of 800 mA, with 17% degradation after 1000 h of operation . The major bottlenecks lie in proper strain management and light extraction. − For AlGaN grown on AlN bulk/templates, the huge misfit strain will trigger the strain relaxation inducing: (1) the generation of misfit dislocations (MDs) which enhance nonradiative recombination; (2) severe phase separation and surface roughness causing local current leakage; − (3) increasing point defects contributing to the nonradiative recombination and current leakage. ,, Although the strain relaxation of AlGaN-based LEDs has been reported widely, − the relaxation mechanisms including the critical condition and triggering sequence for high Al-content AlGaN have been less than decisive. Clarifying the relaxation mechanisms and engineering the misfit strain during AlGaN growth is crucial to defining the final structural quality, which is a vital step toward performance improvement of AlGaN-based UV-B LEDs and potential for practical applications.…”

Section: Introductionmentioning

confidence: 99%

Toward High-Performance AlGaN-Based UV-B LEDs: Engineering of the Strain Relaxation Process

Liu,

Huang

et al. 2024

Crystal Growth & Design

View full text Add to dashboard Cite

Strain management is the key to achieving highquality aluminum gallium nitride (AlGaN) materials for fabricating AlGaN-based ultraviolet-B (UV-B) light-emitting diodes (LEDs). In this work, a kinetic defect evolution model to capture the strain relaxation process for AlGaN growth of UV-B LEDs was demonstrated. The relaxation started from the inclination of threading dislocations (TDs) dominantly over the coexistence of TD inclination, surface roughening, misfit dislocation (MD) generation, enhanced phase separation, etc. as the thickness of n-AlGaN increased. The critical thickness for strain relaxation by TD inclination, MD generation, and the theoretical MD density were obtained. Finally, flip-chip UV-B LEDs with properly engineered buffer strain were fabricated, which showed a maximum light output power of 49.1 mW under 500 mA and a high external quantum efficiency of 3.00% at 310.2 nm, without a high-reflective Rh electrode or any complex packaging process. This work improves our understanding of the relaxation mechanism and prompts further consideration of the strain management in AlGaN-based UV-B LEDs.

show abstract

Origin of defect luminescence in ultraviolet emitting AlGaN diode structures

Cited by 6 publications

References 25 publications

The Influence of Alloy Disorder Effects on the Anisotropy of Emission Diagrams in (Al,Ga)N Quantum Wells Embedded into AlN Barriers

The Influence of Alloy Disorder Effects on the Anisotropy of Emission Diagrams in (Al,Ga)N Quantum Wells Embedded into AlN Barriers

Core–Shell Nanorods as Ultraviolet Light-Emitting Diodes

Toward High-Performance AlGaN-Based UV-B LEDs: Engineering of the Strain Relaxation Process

Contact Info

Product

Resources

About