Optical properties associated with strain relaxations in thick InGaN epitaxial films

Tsai, Wen Che; Hsu, Cheng Hsiung; Fu, S. F.; Lee, Fang Wei; Chen, Chin Yu; Chou, Wu–Ching; Chen, Wei–Kuo; Chang, Wen‐Hao

doi:10.1364/oe.22.00a416

Cited by 16 publications

(6 citation statements)

References 33 publications

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“…Two effects can be considered as a strong driving force of the high In content in the DHS on nanopyramids. One is the difference in the diffusion length between composite atoms, and the other is the compositional pulling effect. − The In adatoms have longer vertical and lateral migration lengths compared to those of the Ga adatoms. This enables In atoms to be more effectively diffused than Ga atoms.…”

Section: Resultsmentioning

confidence: 99%

“…To improve the In incorporation efficiency, introduction of a thick InGaN layer, instead of thin QWs, can be one approach because the In incorporation efficiency is known to increase with the strain relaxation. − In addition, the thick InGaN layer is quite effective to reduce the carrier density by enlarging the active volume, and therefore, it is an efficient way to reduce the efficiency droop problem in group III-nitrides. , However, in general, the use of a thick InGaN layer with high In content is quite inadequate with planar structures. The high In content requires a low growth temperature, and the accumulated strain yields dislocations: therefore, the crystal quality problem arises …”

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confidence: 99%

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Red Emission of InGaN/GaN Double Heterostructures on GaN Nanopyramid Structures

Kim

Gong

et al. 2015

ACS Photonics

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We fabricated InGaN double-hetero structure (DHS) on the nanosized pyramid structure and successfully demonstrated efficient red color emission at 650 nm from this unique structure. The nanosized pyramid structure was fabricated by selective area growth method with nanoimprint. The different diffusion length of composite atoms and compositional pulling effect on the pyramid structure gave rise to not only compositional variation, but also high Incontent InGaN of more than 40%. The InGaN DHS on nanopyramids shows high internal quantum efficiency, sub-ns fast recombination time (negligible built-in electric fields), and less efficiency droop even with the high In content. These results are important to realize efficient red emission based on InGaN material, providing possibilities for efficient photonic devices operating at the long wavelength visible region.

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Section: Resultsmentioning

confidence: 99%

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confidence: 99%

Red Emission of InGaN/GaN Double Heterostructures on GaN Nanopyramid Structures

Kim

Gong

et al. 2015

ACS Photonics

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“…These wavelength non-uniformities result from the formation of localized high-indium-content sections, which prevent diffusion and carrier capture by non-radiative recombination centers [1,[43][44][45]. This would result in higher IQE from regions of the active region with larger potential fluctuations, such as near the apex.…”

Section: Ae Tmentioning

confidence: 99%

Spectrally-resolved internal quantum efficiency and carrier dynamics of semipolar $(10\bar{1}1)$ core-shell triangular nanostripe GaN/InGaN LEDs

et al. 2018

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We investigate the spectrally resolved internal quantum efficiency (IQE) and carrier dynamics in semipolar [Formula: see text] core-shell triangular nanostripe light-emitting diodes (TLEDs) using temperature-dependent photoluminescence (TDPL) and time-resolved photoluminescence (TRPL) at various excitation energy densities. Using electroluminescence, photoluminescence, and cathodoluminescence measurements, we verify the origins of the broad emission spectra from the nanostructures and confirm that localized regions of high-indium-content InGaN exist along the apex of the nanostructures. Spectrally resolved IQE measurements are then performed, with the spectra integrated from 400-450 nm and 450-500 nm to obtain the IQE of the QWs mainly near the sidewalls and apex of the TLEDs, respectively. TDPL and TRPL are used to decouple the radiative and non-radiative carrier lifetimes for different regions of the emission spectra. We observe that the IQE is higher for the spectral region between 450 nm and 500 nm compared to the IQE between 400 and 450 nm. This result is in contrast to the typical observation that the IQE of planar GaN-based LEDs is lower for longer wavelengths (i.e., higher indium contents). We also observe a longer non-radiative recombination lifetime for the longer wavelength portion of the spectrum. Several explanations are proposed for the improved IQE and longer non-radiative lifetime observed near the apex of the nanostructures. The results show that nanostructures may be leveraged to design more efficient green LEDs, potentially addressing a long-standing challenge in GaN-based materials.

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“…18 The stress-relaxed InGaN film is also proven to have more pronounced carrier localization than the strained InGaN film. 34,47 Therefore, both of the improved crystal quality and stress relaxation of the underlying GaN template lead to the stronger carrier localization of MQWs on SCPSS. In light of the above TDPL findings, the reduced TDs and increased localization effects enable more carriers trapped by localized states and fewer by dislocations, leading to the suppressed nonradiative recombination in the MQW sample on SCPSS.…”

Section: Acs Applied Materials and Interfacesmentioning

confidence: 99%

Dislocation Reduction and Stress Relaxation of GaN and InGaN Multiple Quantum Wells with Improved Performance via Serpentine Channel Patterned Mask

Zhang

et al. 2016

ACS Appl. Mater. Interfaces

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The existence of high threading dislocation density (TDD) in GaN-based epilayers is a long unsolved problem, which hinders further applications of defect-sensitive GaN-based devices. Multiple-modulation of epitaxial lateral overgrowth (ELOG) is used to achieve high-quality GaN template on a novel serpentine channel patterned sapphire substrate (SCPSS). The dislocation blocking brought by the serpentine channel patterned mask, coupled with repeated dislocation bending, can reduce the dislocation density to a yet-to-be-optimized level of ∼2 × 10(5) to 2 × 10(6) cm(-2). About 80% area utilization rate of GaN with low TDD and stress relaxation is obtained. The periodical variations of dislocation density, optical properties and residual stress in GaN-based epilayers on SCPSS are analyzed. The quantum efficiency of InGaN/GaN multiple quantum wells (MQWs) on it can be increased by 52% compared with the conventional sapphire substrate. The reduced nonradiative recombination centers, the enhanced carrier localization, and the suppressed quantum confined Stark effect, are the main determinants of improved luminous performance in MQWs on SCPSS. This developed ELOG on serpentine shaped mask needs no interruption and regrowth, which can be a promising candidate for the heteroepitaxy of semipolar/nonpolar GaN and GaAs with high quality.

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Optical properties associated with strain relaxations in thick InGaN epitaxial films

Cited by 16 publications

References 33 publications

Red Emission of InGaN/GaN Double Heterostructures on GaN Nanopyramid Structures

Red Emission of InGaN/GaN Double Heterostructures on GaN Nanopyramid Structures

Spectrally-resolved internal quantum efficiency and carrier dynamics of semipolar $(10\bar{1}1)$ core-shell triangular nanostripe GaN/InGaN LEDs

Dislocation Reduction and Stress Relaxation of GaN and InGaN Multiple Quantum Wells with Improved Performance via Serpentine Channel Patterned Mask

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