Relaxation of InGaN thin layers observed by X-ray and transmission electron microscopy studies

Liliental-Webber, Z.; Benamara, Mourad; Washburn, J.; Domagała, J. Z.; Bak-Misiuk, J.; Piner, Edwin L.; Roberts, John C.; Bedair, S. M.

doi:10.1007/s11664-001-0056-5

Cited by 36 publications

(21 citation statements)

References 18 publications

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“…Despite the extensive studies, however, an abrupt reduction in quantum efficiency occurs for In x Ga 1-x N emitting at blue-green wavelengths longer than $500 nm, which corresponds to increasing indium compositions beyond x $ 0.2. 7 This drop in quantum efficiency in conventional InGaNalloy films has been attributed to multiple underlying mechanisms including [8][9][10][11][12][13][14][15] (a) misfit-dislocation formation driven by lattice mismatch, (b) spinodal-like decomposition driven by thermodynamic immiscibility, (c) poor electron-hole wavefunction overlap driven by piezoelectric and spontaneous polarization, and (d) point-defect incorporation driven by low growth temperatures. These mechanisms all worsen as the In composition increases because the corresponding latticemismatch strain increases and the required InGaN-growth temperature decreases.…”

Section: Introductionmentioning

confidence: 99%

“…31 Since these small systems cannot capture the formation of the larger extended defects observed herein, we will primarily compare our MD simulations to the results selected from the extensive literature experimental studies of defects for both GaN and InGaN. The defects most commonly found during experimental growths of GaN and InGaN include stacking faults and associated mixed polytypism, [33][34][35][36][37][38] domain and grain boundaries, 36,39-41 threading 36,40,[42][43][44][45] and misfit dislocations, 12,[46][47][48][49][50] surface roughness, 43,[51][52][53][54][55][56][57][58] surface-pits (most notably, socalled "V-defects" 59,60 and concatenated V-defect trenches 61 ), and bulk voids. 44,51,62,63 These defects have typically appeared either when growth conditions are poorly optimized (as when these materials and growth processes were first explored) or when conditions are pushed yet farther from equilibrium (as in ongoing attempts to expand or tailor growth-process methods for improved materials).…”

Section: Introductionmentioning

confidence: 99%

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Molecular dynamics studies of defect formation during heteroepitaxial growth of InGaN alloys on (0001) GaN surfaces

Gruber

Zhou

Jones

et al. 2017

Journal of Applied Physics

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We investigate the formation of extended defects during molecular-dynamics (MD) simulations of GaN and InGaN growth on (0001) and ([Formula: see text]) wurtzite-GaN surfaces. The simulated growths are conducted on an atypically large scale by sequentially injecting nearly a million individual vapor-phase atoms towards a fixed GaN surface; we apply time-and-position-dependent boundary constraints that vary the ensemble treatments of the vapor-phase, the near-surface solid-phase, and the bulk-like regions of the growing layer. The simulations employ newly optimized Stillinger-Weber In-Ga-N-system potentials, wherein multiple binary and ternary structures are included in the underlying density-functional-theory training sets, allowing improved treatment of In-Ga-related atomic interactions. To examine the effect of growth conditions, we study a matrix of >30 different MD-growth simulations for a range of In Ga N-alloy compositions (0 ≤ ≤ 0.4) and homologous growth temperatures [0.50 ≤ () ≤ 0.90], where () is the simulated melting point. Growths conducted on polar (0001) GaN substrates exhibit the formation of various extended defects including stacking faults/polymorphism, associated domain boundaries, surface roughness, dislocations, and voids. In contrast, selected growths conducted on semi-polar ([Formula: see text]) GaN, where the wurtzite-phase stacking sequence is revealed at the surface, exhibit the formation of far fewer stacking faults. We discuss variations in the defect formation with the MD growth conditions, and we compare the resulting simulated films to existing experimental observations in InGaN/GaN. While the palette of defects observed by MD closely resembles those observed in the past experiments, further work is needed to achieve truly predictive large-scale simulations of InGaN/GaN crystal growth using MD methodologies.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Molecular dynamics studies of defect formation during heteroepitaxial growth of InGaN alloys on (0001) GaN surfaces

Gruber

Zhou

Jones

et al. 2017

Journal of Applied Physics

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“…Another undesirable property that potentially limits green and longer wavelength LEDs is the InGaN coherency strain limit on c-axis GaN. We have observed (along with other groups [15][16][17]) that the coherency strain limits the amount of indium that is incorporated in the In x Ga 1-x N QW to x ~ 0.2. Even when growth conditions are chosen that favor higher indium incorporation, the InGaN is limited to x ~ 0.2, until the InGaN film strain relaxes.…”

Section: Project Objectivesmentioning

confidence: 59%

“…Using the same MQW growth conditions, we ranked the resultant wavelength for each of the substrates investigated in this program. The shortest wavelengths produced were on the (10-13) which was similar to (11)(12)(13)(14)(15)(16)(17)(18)(19)(20) with increasing wavelengths produced on the (10-10) < (0001) < (10-1-3) < (20-2-1) < (20-21) < (10-11) < (10-1-1). 4).…”

Section: Executive Summarymentioning

confidence: 85%

Semi-polar GaN materials technology for high IQE green LEDs.

Koleske¹,

Lee²,

Crawford³

et al. 2013

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The goal of this NETL funded program was to improve the IQE in green (and longer wavelength) nitride-based LEDs structures by using semi-polar GaN planar orientations for InGaN multiple quantum well (MQW) growth. These semi-polar orientations have the advantage of significantly reducing the piezoelectric fields that distort the QW band structure and decrease electron-hole overlap. In addition, semipolar surfaces potentially provide a more open surface bonding environment for indium incorporation, thus enabling higher indium concentrations in the InGaN MQW. The goal of the proposed work was to select the optimal semi-polar orientation and explore wafer miscuts around this orientation that produced the highest quantum efficiency LEDs. At the end of this program we had hoped to have MQWs active regions at 540 nm with an IQE of 50% and an EQE of 40%, which would be approximately twice the estimated current state-of-the-art.

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“…The direct bandgap of InGaN is used as the active material in optical devices and gives the possibility of obtaining light emission with tunable wavelength, depending on In content. Our earlier studies of In x Ga 1-x N films (0.2 < x < 0.5) grown by MOCVD on c-plane sapphire with a GaN buffer layer using x-ray reciprocal space mapping reflection showed for the first time that these layers are not uniform but are divided into strained and relaxed layers which differ in In composition and structural defect distribution [1]. Only in the relaxed part of the layer did experimental values for In content approach the nominal values.…”

Section: Introductionmentioning

confidence: 99%

Structural defects and cathodoluminescence of In_xGa_1‐xN layers

Liliental‐Weber

Ogletree

et al. 2011

Phys. Status Solidi C

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Correlation between structural defects and appearance of multiple cathodoluminescence and photoluminescence peaks of InxGa1‐xN grown nominally with x = 0.1 and increasing layer thickness (100 nm to 1000 nm) is discussed. Cathodoluminescence studies were performed on the cross‐section samples earlier characterized by electron microscopy including Z‐contrast microscopy. Strained and relaxed layers with different In concentrations were observed for InGaN layers above the critical layer thickness. Stacking faults appear at high density in the relaxed layer which also roughens, created a saw‐tooth surface profile due to V‐shaped pits. Large domains of closely separated stacking faults (polytype‐like) were observed. In Z‐contrast microscopy stacking faults in upper/lower part of the layer appear with higher/lower brightness, suggesting different amount of In incorporation in agreement with x‐ray and RBS results. Only thin, strained InGaN layers showed single band‐edge CL peaks. Multiple CL peaks appear in the relaxed, defective portion of the InGaN layers. By comparison with GaN samples where structural defects are associated with CL peak shifts, we postulate that defects, their type and distribution are main contributors to the multiple peaks observed for InGaN samples (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Relaxation of InGaN thin layers observed by X-ray and transmission electron microscopy studies

Cited by 36 publications

References 18 publications

Molecular dynamics studies of defect formation during heteroepitaxial growth of InGaN alloys on (0001) GaN surfaces

Molecular dynamics studies of defect formation during heteroepitaxial growth of InGaN alloys on (0001) GaN surfaces

Semi-polar GaN materials technology for high IQE green LEDs.

Structural defects and cathodoluminescence of In_xGa_1‐xN layers

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Relaxation of InGaN thin layers observed by X-ray and transmission electron microscopy studies

Cited by 36 publications

References 18 publications

Molecular dynamics studies of defect formation during heteroepitaxial growth of InGaN alloys on (0001) GaN surfaces

Molecular dynamics studies of defect formation during heteroepitaxial growth of InGaN alloys on (0001) GaN surfaces

Semi-polar GaN materials technology for high IQE green LEDs.

Structural defects and cathodoluminescence of InxGa1‐xN layers

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Product

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Structural defects and cathodoluminescence of In_xGa_1‐xN layers