Defect structure in GaN pyramids

Farrer, Jeffrey K.; Carter, C. Barry

doi:10.1007/s10853-006-6563-2

Cited by 17 publications

(12 citation statements)

References 61 publications

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“…2017, 5, 1600804 www.advancedsciencenews.com pyramidal volume, except for a small increase at the base. The increase in the structural defects at the base [35,36] is the likely cause of the increased YL emission. At 720 nm excitation, SHG generated at 360 nm results in the linear absorption of SHG photons into conduction band and subsequent relaxation to shallow states followed by recombination in the shallow donordeep acceptor states resulting in the increase in YL toward the base.…”

Section: Resultsmentioning

confidence: 99%

Hyperspectral Nonlinear Optical Light Generation from a Monolithic GaN Microcavity

Butler

Jiang

Jun

et al. 2017

Advanced Optical Materials

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Localized spatial excitation of a single hexagonal GaN micropyramid with (1 101) facets formed by selective area growth is optimized for nonlinear optical light (NLO) generation due to second harmonic generation (SHG) and multiphoton luminescence (MPL). Multiphoton transition induced ultraviolet and yellow luminescence is observed for excitations above and below half bandgap energy. SHG and MPL observed for excitations below half the bandgap energy are superimposed to realize broadband emission in the UV-visible range. The light generation is optimized by controlling the cavity modes formed by the hexagonal facets and the tip enhanced effects from the pyramid. The MPL is optimum at the apex of the pyramid. The SHG is most efficient within the pyramid (≈4 µm above the base) due to the formation of spatially stable cavity modes within the cavity. The NLO interactions within the pyramid are optimized to realize microphotonic white light sources and coherent tunable UV-visible sources using spatially controlled excitation without any change in material parameters. At the bandgap of GaN, the resonant two-photon emission dominates the nonlinear light generation process compared to the coherent SHG light generated within the cavity.

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Section: Resultsmentioning

confidence: 99%

Hyperspectral Nonlinear Optical Light Generation from a Monolithic GaN Microcavity

Butler

Jiang

Jun

et al. 2017

Advanced Optical Materials

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“…This general behavior is also found for dislocations initially oriented along the [0001] growth direction if inclined facets appear during growth of GaN epitaxial layers. The dislocations then bend toward the inclined facet, [19][20][21]23,25,26,65 in order to minimize the line energy by shortening its length. Note, the dislocations in the cleaved samples likely do not reach their equilibrium line directions after cleavage at room temperature.…”

Section: Determination Of the Depth Of The Dislocation Corementioning

confidence: 99%

“…18 Therefore, the need to reduce the dislocation concentrations has led to growth schemes, where the dislocation lines are bent off the growth direction. [19][20][21][22][23][24][25][26] Hence, most dislocations are not present in their original line direction and may thus change their electronic properties. Therefore, it is particularly relevant to be able to identify the line direction of the dislocation cores.…”

Section: Introductionmentioning

confidence: 99%

Tracking the subsurface path of dislocations in GaN using scanning tunneling microscopy

Weidlich

Schnedler

Portz

et al. 2015

Journal of Applied Physics

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A methodology for the determination of the subsurface line direction of dislocations using scanning tunneling microscopy (STM) images is presented. The depth of the dislocation core is derived from an analysis of the displacement field measured by STM. The methodology is illustrated for dislocations at GaN(10 10) cleavage surfaces. It is found that the dislocation line bends toward the surface, changing from predominantly edge-type to more screw-type character, when approaching the intersection point. Simultaneously, the total displacement detectable at the surface increases due to a preferred relaxation towards the surface. V C 2015 AIP Publishing LLC.

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“…[5][6][7][8][9][10][11][12][13][14][15] The common principle for dislocation reduction is the introduction of interfaces or inclined growth facets, which influence the line directions of threading dislocations. 7,[16][17][18][19][20][21] Inclined facets are also introduced by v-shaped pits or inverted pyramidal defects typically around threading dislocations in epitaxial layers of group III-nitride semiconductors. [22][23][24][25][26][27] These v-shaped defects are delimited by six inclined f11 22g semipolar facets.…”

mentioning

confidence: 99%

“…28 Dislocations were found to bend toward such inclined facets (produced by patterning of the substrates). 7,8,16,18,20,21,29 This attractive interaction was explained by the orientation dependent energy of dislocation lines, 19 the emergence of dislocations at inclined facets combined with the minimization of the length of the dislocation lines, 18 or/and by attractive strain effects due to image forces. 7 Recent images of the etched c growth surfaces suggest that the concentration of dislocations with c line direction component is lower in v-shaped defects than in the surrounding material.…”

mentioning

confidence: 99%

Repulsive interactions between dislocations and overgrown v-shaped defects in epitaxial GaN layers

Weidlich

Schnedler

Eisele

et al. 2013

Applied Physics Letters

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The spatial distribution and the projected line directions of dislocations intersecting a crosssectional ð10 10Þ cleavage plane of a GaN(0001) epitaxial layer is mapped using scanning tunneling microscopy. The data is correlated with the spatial positions of v-shaped defects. The dislocations are found to be bent away from the inclined semipolar facets of v-shaped defects, due to a strain-induced repulsive interaction. The dislocation distribution is characterized by agglomerations and intersecting bundles of dislocations with parallel projected line directions, stabilized by many body effects in the repulsive strain interactions. V

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Defect structure in GaN pyramids

Cited by 17 publications

References 61 publications

Hyperspectral Nonlinear Optical Light Generation from a Monolithic GaN Microcavity

Hyperspectral Nonlinear Optical Light Generation from a Monolithic GaN Microcavity

Tracking the subsurface path of dislocations in GaN using scanning tunneling microscopy

Repulsive interactions between dislocations and overgrown v-shaped defects in epitaxial GaN layers

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