Structural and optical impacts of AlGaN undershells on coaxial GaInN/GaN multiple-quantum-shells nanowires

Lu, Weifang; Terazawa, Mizuki; Han, Dong‐Pyo; Sone, Naoki; Goto, Nanami; Iida, K.; Murakami, Hedeki; Iwaya, Motoaki; Tekeuchi, Tetsuya; Kamiyama, Satoshi; Akasaki, Isamu

doi:10.1515/nanoph-2019-0328

Cited by 13 publications

(22 citation statements)

References 44 publications

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“…The addition of AlGaN underlayer (UL) on core-shell InGaN/GaN MQWs has recently been studied showing an improvement of IQE from 29 to 35%. 21,22 Also, Rishinaramangalam et al demonstrated a reduction of reverse leakage current on wires and triangular stripes covered with InGaN MQWs in presence of AlGaN UL. 23 A further optimized core-shell LED structure including AlGaN UL and electron blocking barrier (EBL) exhibiting an IQE as high as 62% have been reported by the group of Feezell with the demonstration wire-LED having an EQE equal to 8.3%.…”

Section: Introductionmentioning

confidence: 99%

“…For instance, the additional AlGaN UL have been successfully integrated in core-shell InGaN QWs allowing to improve the IQE and EQE of wire-LEDs, as previously mentioned. 21,22,23,24 Hence, the objective of this work is to extend the UL study of m-plane core-shell InGaN MQW systems investigating the influence of GaN and low In-content InGaN pre-growth layers in order to improve the QW luminescence efficiency. The pre-growth of GaN layer aims to improve the crystal structural quality before the QW growth (GaN pre-layer is called "GaN spacer" hereafter).…”

Section: Introductionmentioning

confidence: 99%

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Role of Underlayer for Efficient Core–Shell InGaN QWs Grown on m-plane GaN Wire Sidewalls

Kapoor

Finot

Grenier

et al. 2020

ACS Appl. Mater. Interfaces

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Different types of buffer layers like InGaN underlayer (UL) and InGaN/GaN superlattices are now well-known to significantly improve the efficiency of c-plane InGaN/GaN based light emitting diodes (LEDs). The present work investigates the role of two different kinds of pregrowth layers (low In-content InGaN UL and GaN UL namely "GaN spacer") on the emission of core-shell m-plane InGaN/GaN single quantum well (QW) grown around Si-doped !̅-GaN microwires obtained by silane-assisted MOVPE. According to photo-and cathodoluminescence measurements performed at room temperature, an improved efficiency of light emission at 435 nm with internal quantum efficiency > 15 % has been achieved by adding a GaN spacer prior to the growth of QW. As revealed by scanning transmission electron microscopy, an ultra-thin residual layer containing Si located at the wire sidewall surfaces favors the formation of highdensity of extended defects nucleated at the first InGaN QW. This contaminated residual incorporation is buried by the growth of GaN spacer and avoids the structural defect formation, therefore explaining the improved optical efficiency. No further improvement is observed by adding the InGaN UL to the structure, which is confirmed by comparable values of the effective carrier lifetime estimated from time-resolved (TR) experiments. Contrary to the case of planar cplane QW where the improved efficiency is attributed to a strong decrease of point defects, the addition of an InGaN UL seem to have no influence in the case of radial m-plane QW.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Role of Underlayer for Efficient Core–Shell InGaN QWs Grown on m-plane GaN Wire Sidewalls

Kapoor

Finot

Grenier

et al. 2020

ACS Appl. Mater. Interfaces

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“…However, up to now, the application of AlGaN as spacers within coaxial GaInN/GaN MQS nanowires has not yet been reported in the literature. Nevertheless, we preliminarily studied the effect of a thin AlGaN layer prior to the MQS structures growth, which showed an improvement in emission efficiency and reduction in the nonradiative recombination rate. , The structural and optical features of coaxial MQS nanowires demonstrated that the AlGaN undershell played an important role to suppress the diffusion of point defects from n -cores to MQS structures. Moreover, an n-type AlGaN undershell was used to suppress the contamination of silicon and oxygen impurities (from the SiN mask) in the p-GaN layer, which resulted in the reduction of reverse leakage current in coaxial nanowire LEDs .…”

Section: Introductionmentioning

confidence: 99%

Correlation between Optical and Structural Characteristics in Coaxial GaInN/GaN Multiple Quantum Shell Nanowires with AlGaN Spacers

Miyamoto

Okuda

et al. 2020

ACS Appl. Mater. Interfaces

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High crystalline quality coaxial GaInN/GaN multiple quantum shells (MQSs) grown on dislocation-free nanowires are highly in demand for efficient white-/micro-light-emitting diodes (LEDs). Here, we propose an effective approach to improve the MQS quality during the selective growth by metal–organic chemical vapor deposition. By increasing the growth temperature of GaN barriers, the cathodoluminescent intensity yielded enhancements of 0.7 and 3.9 times in the samples with GaN and AlGaN spacers, respectively. Using an AlGaN spacer before increasing the barrier temperature, the decomposition of GaInN quantum wells was suppressed on all planes, resulting in a high internal quantum efficiency up to 69%. As revealed by scanning transmission electron microscopy (STEM) characterization, the high barrier growth temperature allowed to achieve a clear interface between GaInN quantum wells and GaN quantum barriers on the c-, r-, and m-planes of the nanowires. Moreover, the correlation between the In incorporation and structure features in MQS was quantitatively assessed based on the STEM energy-dispersive X-ray spectroscopy mapping and line-scan profiles of In and Al fractions. Ultimately, it was demonstrated that the unintentional In incorporation in GaN barriers was induced by the evaporation of predeposited In-rich particles during low-temperature growth of GaInN wells. Such residual In contamination was sufficiently inhibited by inserting low Al fraction (∼6%) AlGaN spacers after each GaInN well. During the growth of AlGaN spacers, AlN polycrystalline particles were deposited on the surrounding dummy substrate, which suppressed the evaporation of the predeposited In-rich particles. Thus, the presence of AlGaN spacers certainly improved the uniformity of In fraction through five GaInN quantum wells and reduced the diffusion of point defects from n-core to MQS active structures. The superior coaxial GaInN/GaN MQS structures with the AlGaN spacer are supposed to improve the emission efficiency in white-/micro-LEDs.

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“…These defects may be due to the low crystal quality of active layers on the c ‐plane of the NWs. [ 41–43 ]…”

Section: Resultsmentioning

confidence: 99%

“…These defects may be due to the low crystal quality of active layers on the c-plane of the NWs. [41][42][43] In region (ii), the defects originating from the m-plane of NW-MQS form on the basal plane (c-plane) and propagate along the m-axis direction, which is a lateral growth direction (indicated by region (ii) in Figure 5). Two types of defect contrasts are observed: defect contrasts that propagated to the coalescence region (indicated by z in Figure 5a) and those that terminate in the GaN layers (indicated by u in Figure 5a).…”

Section: Structural Evaluation and Defect Distribution Analysis Of Th...mentioning

confidence: 99%

Growth Defects in InGaN‐Based Multiple‐Quantum‐Shell Nanowires with Si‐Doped GaN Cap Layers and Tunnel Junctions

Okuno

Mizutani

Iida

et al. 2022

Physica Status Solidi (b)

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Herein, the growth mechanism and defect structure of GaN‐based nanowire multiple‐quantum‐shells (NW‐MQSs) with cap layers combining tunnel junctions and n‐GaN are investigated in detail. In the NW‐MQS structure, defect structures are formed in three regions: (i) From the c‐plane active layer at the tip of NW because of the low crystal quality of the active layer. (ii) Basal‐plane stacking faults (BSFs) with partial dislocations (PDs) are generated from the m‐planes of the NW‐MQSs; these defects are triggered by the silicon nitride (SiNx) formed on the NW surface. While some defects terminate because of the half loop formed by the PDs along the lateral growth of cap layers, others terminate at the coalesced region of the cap layers grown from adjacent MQSs. (iii) Line defects due to low‐angle grain boundaries and planar defects due to the BSFs in region (ii) are formed in the region wherein cap layers coalesce. The defects reaching the surface of the cap layers predominantly depend on the number of defects generated from the c‐plane active layers in region (i). The growth mode and propagation mechanism of such defects are associated, and a method for realizing optical devices based on the high‐quality NW‐MQS structures is discussed.

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Structural and optical impacts of AlGaN undershells on coaxial GaInN/GaN multiple-quantum-shells nanowires

Cited by 13 publications

References 44 publications

Role of Underlayer for Efficient Core–Shell InGaN QWs Grown on m-plane GaN Wire Sidewalls

Role of Underlayer for Efficient Core–Shell InGaN QWs Grown on m-plane GaN Wire Sidewalls

Correlation between Optical and Structural Characteristics in Coaxial GaInN/GaN Multiple Quantum Shell Nanowires with AlGaN Spacers

Growth Defects in InGaN‐Based Multiple‐Quantum‐Shell Nanowires with Si‐Doped GaN Cap Layers and Tunnel Junctions

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