Pulsed atomic-layer epitaxy of ultrahigh-quality AlxGa1−xN structures for deep ultraviolet emissions below 230 nm

Zhang, J. P.; Sun, Wenhong; Wang, H. M.; Chen, C. Q.; Fareed, Q.; Kuokštis, E.; Yang, Jun

doi:10.1063/1.1528726

Cited by 133 publications

(81 citation statements)

References 26 publications

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“…As investigated by Kueller et al 18 , a smooth crack free overgrown AlN layer can only be formed when the stripes are orientated in the (1-100) direction. Whereas the (11)(12)(13)(14)(15)(16)(17)(18)(19)(20) direction will give a strongly faceted surface, leading to inhomogeneous Al distribution in AlGaN layers grown subsequently in UV LED devices. The orientation requirements for this patterning demands a high level expertise in expensive lithography alignment and additional processing steps.…”

Section: Introductionmentioning

confidence: 99%

“…9 Essentially the AlN buffer layer needs to have a very low TDD so that very few dislocations reach the subsequent active region. Engineering the growth conditions such as pulsed-flow 10,11 and migration enhanced MOVPE (MEMOVPE) 12,13 have been used to reduce TDDs affecting mostly the screw type dislocations. In-situ MOVPE growth engineering has little effect however on the edge and mixed 2 | J.…”

Section: Introductionmentioning

confidence: 99%

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Epitaxial lateral overgrowth of AlN on self-assembled patterned nanorods

Conroy

Zubialevich

et al. 2015

J. Mater. Chem. C

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We report an inexpensive nanoscale patterning process for epitaxial lateral overgrowth (ELOG) in AlN layers grown by metal organic vapour phase epitaxy (MOVPE) on sapphire. The pattern was produced by an inductively coupled plasma etch using a self-assembled monolayer of silica spheres on AlN as the lithographic mask. The resulting uniform 1 [small mu ]m length rod structure across a wafer showed a massive reduction in threading dislocations (TDs) when annealed at 1100 [degree]C. Overgrowing homoepitaxial AlN on top of the nanorods, at a temperature of 1100 [degree]C, produced a crack free coalesced film with approximately 4 [small mu ]m of growth, which is formed at a much lower temperature compared to that typically required for microscale ELOG. The improved crystal quality, in terms of TD reduction, of the AlN above the rods was determined by detailed weak beam (WB) electron microscopy studies and showed that the threading dislocation density (TDD) was greatly reduced, by approximately two orders of magnitude in the case for edge-type dislocations. In situ reflectance measurements during the overgrowth allowed for thickness coalescence to be estimated along with wafer curvature changes. The in situ measurements also confirmed that tensile strain built up at a much slower rate in the ELOG AlN layer compared to that of AlN prepared directly on sapphire

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Epitaxial lateral overgrowth of AlN on self-assembled patterned nanorods

Conroy

Zubialevich

et al. 2015

J. Mater. Chem. C

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“…On the other hand, the enhancement of the surface mobility of Al is especially important for high quality AlGaN layers (Zhao et al, 2006b(Zhao et al, , 2008a. The migration-enhanced MOCVD is intended to carry on for improving the surface dynamic behavior of Al atoms in the growth (Zhang et al, 2002). …”

Section: Parasitic Reaction Between Tmal and Nh 3 In Mocvdmentioning

confidence: 99%

GaN Based Ultraviolet Photodetectors

Zhao¹,

Jiang²

2011

Photodiodes - World Activities in 2011

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“…[56] In order to obtain AlN and high Al-molar fraction AlGaN with high crystalline quality and flat surface morphology by using moderate growth temperatures, pulsed-flow growth methods, which can effectively promote the surface migration of Al (and Ga and In) adatoms, have been developed instead of the conventional continuous growth. There are at least three types of pulsed-flow growth methods, namely (a) NH3 pulse-flow growth, [17,60] (b) pulsed atomic layer epitaxy (PALE), [61,62] and (c) migration-enhanced metalorganic chemical vapor deposition (MEMOCVD), [63,64] as shown schematically in Figure 5. For the NH3 pulse-flow growth of AlN, pulsed NH3 flow was employed to enhance the lateral migration of Al adatoms, while TMAl flow was kept constant during the NH3 pulsed-flow sequence to ensure Al-rich growth conditions.…”

Section: Pulsed-flow Growth Of Aln and High Al-molar Fraction Alganmentioning

confidence: 99%

“…This method allows accurate control of the quaternary layer composition and thickness by simply changing the number of aluminum, indium, and gallium pulses in a unit cell and the number of unit cell repeats. [61,62] MEMOCVD is carried out at relatively high temperatures (>1200 °C) and low reactor pressure conditions (<100 Torr). In contrast to PALE, the duration and waveforms of precursor pulses in MEMOCVD can be partially overlapped, allowing for a continuum of growth technique ranging from atomic layer epitaxy to conventional MOCVD.…”

Section: Pulsed-flow Growth Of Aln and High Al-molar Fraction Alganmentioning

confidence: 99%

Status of Growth of Group III-Nitride Heterostructures for Deep Ultraviolet Light-Emitting Diodes

Ding¹,

Avrutin²,

Özgür³

et al. 2017

Preprint

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Abstract:We overview recent progress in growth aspects of group III-nitride heterostructures for deep ultraviolet (DUV) light-emitting diodes (LEDs), with particular emphasis on the growth approaches for attaining high-quality AlN and high Al-molar fraction AlGaN. The discussion commences with the introduction of the current status of group III-nitride DUV LEDs and the remaining challenges. This segues into discussion of LED designs enabling high device performance followed by the review of advances in the methods for the growth of bulk single crystal AlN intended as a native substrate together with a discussion of its UV transparency. It should be stated, however, that due to the high-cost of bulk AlN substrates at the time of this writing, the growth of DUV LEDs on foreign substrates such as sapphire still dominates the field. On the deposition front, the heteroepitaxial growth approaches incorporate high-temperature metal organic chemical vapor deposition (MOCVD) and pulsed-flow growth, a variant of MOCVD, with the overarching goal of enhancing adatom surface mobility, and thus epitaxial lateral overgrowth which culminates in minimization the effect of lattice-and thermal-mismatches. This is followed by addressing the benefits of pseudomorphic growth of strained high Al-molar fraction AlGaN on AlN. Finally, methods utilized to enhance both p-and n-type conductivity of high Al-molar fraction AlGaN are reviewed.

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Pulsed atomic-layer epitaxy of ultrahigh-quality AlxGa1−xN structures for deep ultraviolet emissions below 230 nm

Cited by 133 publications

References 26 publications

Epitaxial lateral overgrowth of AlN on self-assembled patterned nanorods

Epitaxial lateral overgrowth of AlN on self-assembled patterned nanorods

GaN Based Ultraviolet Photodetectors

Status of Growth of Group III-Nitride Heterostructures for Deep Ultraviolet Light-Emitting Diodes

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