Gallium nitride and related materials: challenges in materials processing

Davis, R. F.; Einfeldt, S.; Preble, E. A.; Roskowski, A. M.; Reitmeier, Z. J.; Miraglia, P.Q.

doi:10.1016/j.actamat.2003.08.005

Cited by 63 publications

(30 citation statements)

References 57 publications

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“…By in situ electroluminescence, dislocations are observed to glide across SiC p-n diodes [4]. In GaN based optical devices, dislocations are found in the active device region in concentrations greater than 9 10 cm 2 - [5]. Dislocations are used to getter metals [6].…”

Section: Introductionmentioning

confidence: 96%

Structure and energy of the partial dislocation cores in GaAs

Beckman

Chrzan

2006

Physica Status Solidi (b)

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A methodology for investigating isolated α and β partial dislocations in III-V semiconductors is presented. Using this method the 30° and 90°, α and β partial dislocations in GaAs are investigated. The structures of the proposed core reconstructions are investigated. For the 90° partials, two reconstructions have been proposed. The relative energies of the two reconstructions are investigated in addition to the structural investigation.

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Section: Introductionmentioning

confidence: 96%

Structure and energy of the partial dislocation cores in GaAs

Beckman

Chrzan

2006

Physica Status Solidi (b)

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“…GaN cannot be directly grown on SiC (Refs. [15][16][17][18] at the normal deposition temperatures used to produce nitridebased LED structures. Instead, a nucleation layer must be grown that is sufficiently closely matched in chemistry, crystallography, lattice parameters, and the coefficients of thermal expansion with the substrate and the subsequently grown layer.…”

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confidence: 99%

Layer-by-layer thermal conductivities of the Group III nitride films in blue/green light emitting diodes

Huang

Liu

et al. 2012

Applied Physics Letters

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Thermal conductivities (k) of the individual layers of a GaN-based light emitting diode (LED) were measured along [0001] using the 3-omega method from 100-400 K. Base layers of AlN, GaN, and InGaN, grown by organometallic vapor phase epitaxy on SiC, have effective k much lower than bulk values. The 100 nm thick AlN layer has k ¼ 0.93 6 0.16 W/mK at 300 K, which is suppressed >100 times relative to bulk AlN. Transmission electron microscope images revealed high dislocation densities (4 Â 10 10 cm À2 ) within AlN and a severely defective AlN-SiC interface that cause additional phonon scattering. Resultant thermal resistances degrade LED performance and lifetime making layer-by-layer k, a critical design metric for LEDs. More than 20% of electricity in the United States is consumed by lighting. Solid-state light emitting diodes (LEDs) hold considerable potential to be more efficient and effective sources of artificial light than incandescent and fluorescent technologies. 1 Group III nitride-based blue and green LEDs are currently being developed for this purpose. Device architectures consist of light-emitting multiple quantum wells (MQWs) supported by base layers of aluminum nitride (AlN), gallium nitride (GaN), and indium gallium nitride (InGaN). The MQW itself is a periodic structure composed of alternating InGaN wells and GaN barriers.Heat generation and removal in the LED are complicated by multiple interfaces, causing high operating temperatures that degrade efficiency, shift the emission spectrum, and reduce the lifetime of LEDs. 2 Prior experimental investigations of bulk GaN and AlN have shown that thermal transport is phonon-dominated. [3][4][5][6] Previous thin film studies have been (i) based on ideal films with low defect concentrations that are unrepresentative of LED grade films 3,7 or (ii) focused on high electron mobility transistors (HEMTs), rather than LED architectures. [8][9][10] Neither submicron GaN films nor real nitride based LED devices have been investigated.Studies of Si and other thin films have demonstrated that thermal conductivity is greatly reduced when the thickness of the film or the defect spacing is less than the intrinsic mean free path of the phonons. 5,11,12 Nitride based LED structures are fabricated from multiple layers of thin films ranging from 3 nm to 100 nm in thickness; whereas, the spectrum-average phonon mean free path in GaN at 300 K is $100 nm, 13 and the longest phonon mean free paths in the spectrum are much greater. 14 To achieve economic viability, the nitride films are grown by organometallic vapor phase epitaxy (OMVPE) on foreign substrates, including SiC, sapphire, and Si. Mismatched lattice constants at the filmsubstrate interface create high densities of atomic and line defects, the latter of which that extend throughout the device as a source of phonon scattering. Given these considerations, this paper reports layer-by-layer experimental measurements of thermal conductivity in real nitride based LED architectures grown on [0001]-oriented SiC substrates. Th...

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“…Growths of monocrystalline IIInitride boules from which wafers can be obtained have not been achieved [4]. Owing to the current need to grow on lattice-mismatched substrates, the typically epitaxially grown III-nitride materials are known to exhibit a high density of dislocations in the 10 9 -10 10 cm À2 range [5], which deteriorate the optoelectronic and transport properties of GaNbased films [6,7].…”

Section: Introductionmentioning

confidence: 99%

“…Owing to the current need to grow on lattice-mismatched substrates, the typically epitaxially grown III-nitride materials are known to exhibit a high density of dislocations in the 10 9 -10 10 cm À2 range [5], which deteriorate the optoelectronic and transport properties of GaNbased films [6,7]. For example, the threading dislocations (TDs) are conduits for charge breakdown of rectifying contacts, act as non-radiative recombination centers and reduce significantly the lifetime of laser diodes (LDs) [4]. Thus the reduction of dislocation density in the GaN crystals is necessary to improve the performance of LD devices [8].…”

Section: Introductionmentioning

confidence: 99%