MOVPE growth of n-GaN cap layer on GaInN/GaN multi-quantum shell LEDs

Goto, Nanami; Sone, Naoki; Iida, K.; Suzuki, Atsushi; Murakami, Hideki; Terazawa, Mizuki; Ohya, Masaki; Kamiyama, Satoshi; Takeuchi, Tetsuya; Akasaki, Isamu

doi:10.1016/j.jcrysgro.2020.125571

Cited by 7 publications

(9 citation statements)

References 21 publications

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“…Meanwhile, the In atom density gradually decreases from one GaInN well toward the GaN barrier. Such a phenomenon was likewise observed in our previous work and has been successfully solved using a modified growth sequence with AlGaN spacers and a high barrier growth temperature. , …”

Section: Results and Discussionmentioning

confidence: 99%

“…A rough surface n-GaN cap layer is not beneficial for the formation of a metallic contact or for the uniform deposition of an insulating film during the device fabrication process. To improve the surface flatness and suppress the voids between the nanowires, the growth conditions of the n-GaN cap layer were further optimized based on extensive experimentation, as reported in our previous work and shown in the results in Figures S1–S5. The two-step growth of the thick n-GaN cap layer was carried out, including a high and a low growth rate of the n-GaN cap layer using different V/III ratios or temperatures.…”

Section: Experimental Sectionmentioning

confidence: 99%

“…For comparison, Sample C was prepared with an extremely low V/III ratio of 44 to suppress the strong hydrogen passivation on r- planes and the formation of voids. Such an adjustment was inspired by the aforementioned growth condition for the n-GaN core and the initial results from our previous work with different V/III ratios for the n-GaN cap layer . In Sample D, the V/III ratio of the second step of the n-GaN cap was decreased from 6000 to 3300, aiming to increase the growth rate and reduce the density of pits on the surface.…”

Section: Experimental Sectionmentioning

confidence: 99%

“…Taking advantage of a thin p-GaN shell, the tunnel effect, and an n-GaN cap layer, low optical loss and low resistance current diffusion could be potentially achieved in MQS nanowire-based devices . However, there are currently very few works published on the application of tunnel junctions in MQS nanowire structures, , especially regarding the characterization of the tunnel junction and the subsequent n-GaN cap growth on core–shell structures.…”

Section: Introductionmentioning

confidence: 99%

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Crystal Growth and Characterization of n-GaN in a Multiple Quantum Shell Nanowire-Based Light Emitter with a Tunnel Junction

Miyamoto

Sone

et al. 2021

ACS Appl. Mater. Interfaces

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Here, we systematically investigated the growth conditions of an n-GaN cap layer for nanowire-based light emitters with a tunnel junction. Selective-area growth of multiple quantum shell (MQS)/nanowire core−shell structures on a patterned n-GaN/sapphire substrate was performed by metal− organic vapor phase epitaxy, followed by the growth of a p-GaN, an n ++ / p ++ -GaN tunnel junction, and an n-GaN cap layer. Specifically, two-step growth of the n-GaN cap layer was carried out under various growth conditions to determine the optimal conditions for a flat n-GaN cap layer. Scanning transmission electron microscopy characterization revealed that n ++ -GaN can be uniformly grown on the m-plane sidewall of MQS nanowires. A clear tunnel junction, involving 10-nm-thick p ++ -GaN and 3-nm-thick n ++ -GaN, was confirmed on the nonpolar m-planes of the nanowires. The Mg doping concentration and distribution profile of the p ++ -GaN shell were inspected using three-dimensional atom probe tomography. Afterward, the reconstructed isoconcentration mapping was applied to identify Mg-rich clusters. The density and average size of the Mg clusters were estimated to be approximately 4.3 × 10 17 cm −3 and 5 nm, respectively. Excluding the Mg atoms contained in the clusters, the remaining Mg doping concentration in the p ++ -GaN region was calculated to be 1.1 × 10 20 cm −3 . Despite the lack of effective activation, a reasonably low operating voltage and distinct light emissions were preliminarily observed in MQS nanowire-based LEDs under the optimal n-GaN cap growth conditions. In the fabricated MQS-nanowire devices, carriers were injected into both the r-plane and m-plane of the nanowires without a clear quantum confinement Stark effect.

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Section: Results and Discussionmentioning

confidence: 99%

Section: Experimental Sectionmentioning

confidence: 99%

Section: Experimental Sectionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Crystal Growth and Characterization of n-GaN in a Multiple Quantum Shell Nanowire-Based Light Emitter with a Tunnel Junction

Miyamoto

Sone

et al. 2021

ACS Appl. Mater. Interfaces

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“…These cap layers are either p-type GaN layers [29] or n-type combined with tunnel junctions (TJs). [30][31][32][33][34][35] Thicker GaN cap layers are required for embedding an NW-MQS with a height of %1 μm. Therefore, p-GaN layers with high electrical resistance and high light absorption are not ideal cap layers.…”

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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Optimization of In‐Reactor In Situ Activation Annealing Conditions for Tunnel Junction Layers in Multiquantum Shell GaN‐Based Devices

Takahashi,

Yamanaka,

et al. 2024

Physica Status Solidi (b)

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For realizing room‐temperature continuous‐wave operation in core–shell GaN nanowire‐based semiconductor lasers, certain device characteristics are required, namely, a low threshold current and low operating voltage. To reduce the operating voltage and inject current into the m‐plane multiquantum shell (MQS) active region, a new structure with a tunnel junction and embedded n‐GaN is proposed. One of the problems in this proposed device architecture is the high resistance at the tunnel junction layer due to hydrogen passivation in the insufficiently activated p‐GaN shell. In situ activation annealing and suppression of re‐passivation during subsequent growth are necessary to reduce the operating voltage. Herein, the time and temperature dependence of in situ activation annealing in a reactor to lower the resistance of tunnel junction layers grown on nanowires with nonpolar m‐planes is investigated. Subsequent n+‐GaN growth is implemented at 550 °C. As a result, the turn‐on voltage is observed to be dependent on the activation annealing time and temperature. The lowest turn‐on voltage is ≈5.4 V at an activation annealing time of 30 min and activation annealing temperature of 800 °C.

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MOVPE growth of n-GaN cap layer on GaInN/GaN multi-quantum shell LEDs

Cited by 7 publications

References 21 publications

Crystal Growth and Characterization of n-GaN in a Multiple Quantum Shell Nanowire-Based Light Emitter with a Tunnel Junction

Crystal Growth and Characterization of n-GaN in a Multiple Quantum Shell Nanowire-Based Light Emitter with a Tunnel Junction

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

Optimization of In‐Reactor In Situ Activation Annealing Conditions for Tunnel Junction Layers in Multiquantum Shell GaN‐Based Devices

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