Silicon induced defect reduction in AlN template layers for epitaxial lateral overgrowth

Mogilatenko, A.; Knauer, A.; Zeimer, U.; Hartmann, C.; Oppermann, Hermann; Weyers, M.

doi:10.1016/j.jcrysgro.2016.12.099

Cited by 10 publications

(5 citation statements)

References 27 publications

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“…The fusion and annihilation of inclined dislocations is a useful technology for reducing dislocation density in semiconductor layers grown on foreign substrates. The most straightforward ways to achieve dislocation inclination in AlN are with reduced growth temperatures [105,106], increased V/III ratios [107], and silicon doping [108]. We have shown that TD inclination and TDD reduction can be produced in AlN grown on SiC through the use of growth conditions with high growth pressure, reduced temperature, and increased V/III ratio [105].…”

Section: Threading Dislocation Density Reduction Methodsmentioning

confidence: 97%

“…It should be noted that this relaxation effect is not caused by the compressive stress, and is rather a mechanism of tensile stress generation which occurs in nearly all c-axis nitride growth. Dislocation inclination is enhanced by Si doping [108,157], and can lead to tensile stress well beyond full relaxation [158], going even into significant tension and cracking. This effect is relevant for samples with high dislocation densities and high resistivity, because high resistivity films must be grown very thick to achieve low sheet resistance.…”

Section: Bulk Resistivity Of N-alganmentioning

confidence: 99%

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Germicidal ultraviolet LEDs: a review of applications and semiconductor technologies

Zollner

DenBaars

Speck

et al. 2021

Semicond. Sci. Technol.

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Ultraviolet light emitting diodes (UV LEDs) are one of the most promising technologies for preventing future pandemics, improving health outcomes, and disinfecting water sources. Currently available UV LEDs emitting in the conventional germicidal wavelength range (254–285 nm) have efficiencies below 5% and cost about 100 times more (per watt) than mercury vapor lamps. On the other hand, germicidal UV LEDs provide many advantages over vapor lamps including instant-on and dimmable functionality, wavelength tunability, miniaturization, and durability, and are already in widespread use for certain applications. It is expected that III-nitride based UV LEDs will soon have similar cost and efficiency to white LEDs and will become the dominant germicidal light source within this decade. Unlike vapor discharge lamps, LEDs have theoretical efficiency limits approaching 100%; the challenges to improving UV LED efficiency are not fundamental, but technological. Improvements in material quality, chemical purity, electrical conductivity, optical transparency, and fabrication technologies are needed. In this review, we outline the major challenges in each of these areas and summarize the recent advances that have enabled rapid improvements in UV LED efficiency within the past 5 years. We discuss the physical principles underlying the mechanisms of improved efficiency, and comment on likely future trends in UV LED design and commercialization.

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Section: Threading Dislocation Density Reduction Methodsmentioning

confidence: 97%

Section: Bulk Resistivity Of N-alganmentioning

confidence: 99%

Germicidal ultraviolet LEDs: a review of applications and semiconductor technologies

Zollner

DenBaars

Speck

et al. 2021

Semicond. Sci. Technol.

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“…First, any optical absorption will be increased with layer thickness. Second, dislocation inclination in epitaxial Si-doped AlGaN is known to lead to residual tension causing wafer bow or cracking [7][8][9], which are detrimental to device operation. Third, if growth conditions are not precisely optimized, surface morphology may worsen with increasing thickness, degrading active region performance.…”

Section: Introductionmentioning

confidence: 99%

Highly Conductive n-Al0.65Ga0.35N Grown by MOCVD Using Low V/III Ratio

et al. 2021

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Highly conductive silicon-doped AlGaN and ohmic contacts are needed for deep-UV LEDs and ultrawide bandgap electronics. We demonstrate improved n-Al0.65Ga0.35N films grown by metal–organic chemical vapor deposition (MOCVD) on sapphire substrates using a low V/III ratio (V/III = 10). A reduced V/III ratio improves repeatability and uniformity by allowing a wider range of silicon precursor flow conditions. AlxGa1−xN:Si with x > 0.5 typically has an electron concentration vs. silicon concentration trend that peaks at a particular “knee” value before dropping sharply as [Si] continues to increase (self-compensation). The Al0.65Ga0.35N:Si grown under the lowest V/III conditions in this study does not show the typical knee behavior, and instead, it has a flat electron concentration trend for [Si] > 3 × 1019 cm−3. Resistivities as low as 4 mΩ-cm were achieved, with corresponding electron mobility of 40 cm2/Vs. AFM and TEM confirm that surface morphology and dislocation density are not degraded by these growth conditions. Furthermore, we report vanadium-based ohmic contacts with a resistivity of 7 × 10−5 Ω-cm2 to AlGaN films grown using a low V/III ratio. Lastly, we use these highly conductive silicon-doped layers to demonstrate a 284 nm UV LED with an operating voltage of 7.99 V at 20 A/cm2, with peak EQE and WPE of 3.5% and 2.7%, respectively.

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“…Silicon is not only necessary for n-type conductivity. Depending on its concentration and growth conditions it can cause a number of different effects on the layer structure: it has been shown to decrease the density of group-III vacancies [8][9][10], to induce tilting of dislocations [11], and to either reduce or improve material quality at high concentrations [12]. Furthermore, depending on the growth process Si was reported to act either as a surfactant [13] or an anti-surfactant [14,15].…”

Section: Introductionmentioning

confidence: 99%

Influence of silicon doping on internal quantum efficiency and threshold of optically pumped deep UV AlGaN quantum well lasers

Jeschke¹,

Mogilatenko²,

Netzel³

et al. 2018

Semicond. Sci. Technol.

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The influence of silicon doping on optically pumped AlGaN quantum well (QW) lasers has been analyzed. Either the QWs, quantum barriers, or the whole heterostructure were doped with Si concentrations between 6×10 16 and 1×10 19 cm −3 . When the QWs are doped up to 5×10 17 cm −3 , laser threshold is reduced and internal quantum efficiency is increased most probably due to a reduction of group-III-vacancies during growth. Higher Si concentrations in the wells can increase the density of group-III-vacancies causing an increased laser threshold. High concentrations can also enhance band gap inhomogeneities and the free carrier density, which improves the internal quantum efficiency measured by photoluminescence. Doping of all layers with a Si concentration of 1×10 19 cm −3 deteriorates the QW quality, most probably because the silicon acts as an anti-surfactant reducing and delaying Ga incorporation.

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Silicon induced defect reduction in AlN template layers for epitaxial lateral overgrowth

Cited by 10 publications

References 27 publications

Germicidal ultraviolet LEDs: a review of applications and semiconductor technologies

Germicidal ultraviolet LEDs: a review of applications and semiconductor technologies

Highly Conductive n-Al0.65Ga0.35N Grown by MOCVD Using Low V/III Ratio

Influence of silicon doping on internal quantum efficiency and threshold of optically pumped deep UV AlGaN quantum well lasers

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