Optimization of low temperature GaN buffer layers for halide vapor phase epitaxy growth of bulk GaN

Hemmingsson, Carl; Pozina, Galia

doi:10.1016/j.jcrysgro.2012.12.016

Cited by 28 publications

(15 citation statements)

References 30 publications

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“…On the other hand, the data clearly indicate a way to reduce the droop in these LEDs in the future, via a drastic reduction of the dislocation density common to the mainstream white LED designs, due to the growth on a foreign substrate. This can be done by using bulk substrates, 16,17 with a sufficiently low dislocation density.…”

Section: -3mentioning

confidence: 99%

Dislocation related droop in InGaN/GaN light emitting diodes investigated via cathodoluminescence

Pozina

Ciechonski

et al. 2015

Applied Physics Letters

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Todays energy saving solutions for general illumination rely on efficient white light emitting diodes (LEDs). However, the output efficiency droop experienced in InGaN based LEDs with increasing current injection is a serious limitation factor for future development of bright white LEDs. We show using cathodoluminescence (CL) spatial mapping at different electron beam currents that threading dislocations are active as nonradiative recombination centers only at high injection conditions. At low current, the dislocations are inactive in carrier recombination due to local potentials, but these potentials are screened by carriers at higher injection levels. In CL images, this corresponds to the increase of the dark contrast around dislocations with the injection (excitation) density and can be linked with droop related to the threading dislocations. Our data indicate that reduction of droop in the future efficient white LED can be achieved via a drastic reduction of the dislocation density by using, for example, bulk native substrates. (C) 2015 AIP Publishing LLC.

Funding Agencies|Swedish Research Council (VR); Swedish Energy Agency

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Section: -3mentioning

confidence: 99%

Dislocation related droop in InGaN/GaN light emitting diodes investigated via cathodoluminescence

Pozina

Ciechonski

et al. 2015

Applied Physics Letters

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Funding Agencies|Swedish Research Council (VR); Swedish Energy Agency

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“…8 Fabrication of large area GaN substrates with a relatively low concentration of impurities (still barely available) has so far been done by halide vapor phase epitaxy (HVPE). [15][16][17] Unintentionally doped HVPE GaN has a moderate concentration of the residual donors (i.e., silicon and oxygen) of $10 17 cm…”

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confidence: 99%

Optical properties of C-doped bulk GaN wafers grown by halide vapor phase epitaxy

Khromov

Hemmingsson

Ḿonemar

et al. 2014

Journal of Applied Physics

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Optical and structural studies of homoepitaxially grown m-plane GaN Appl. Phys. Lett. 100, 172108 (2012) Freestanding bulk C-doped GaN wafers grown by halide vapor phase epitaxy are studied by optical spectroscopy and electron microscopy. Significant changes of the near band gap (NBG) emission as well as an enhancement of yellow luminescence have been found with increasing C doping from 5 Â 10 16 cm À3 to 6 Â 10 17 cm À3. Cathodoluminescence mapping reveals hexagonal domain structures (pits) with high oxygen concentrations formed during the growth. NBG emission within the pits even at high C concentration is dominated by a rather broad line at $3.47 eV typical for n-type GaN. In the area without pits, quenching of the donor bound exciton (DBE) spectrum at moderate C doping levels of 1-2 Â 10 17 cm À3 is observed along with the appearance of two acceptor bound exciton lines typical for Mg-doped GaN. The DBE ionization due to local electric fields in compensated GaN may explain the transformation of the NBG emission. V C 2014 AIP Publishing LLC.

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“…HVPE is the most popular way for free-standing GaN growth due to the very high growth rate (typical around 200 to 500 µm/h in the c-direction) [86,87] and low cost.…”

Section: The Aspect Of Gan Epitaxy Substrate Selectionmentioning

confidence: 99%

CVD solutions for new directions in SiC and GaN epitaxy

Li¹

2015

Linköping Studies in Science and Technology. Dissertations

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This thesis aims to develop a chemical vapor deposition (CVD) process for the new directions in both silicon carbon (SiC) and gallium nitride (GaN) epitaxial growth. The properties of the grown epitaxial layers are investigated in detail in order to have a deep understanding. SiC is a promising wide band gap semiconductor material which could be utilized for fabricating high-power and high-frequency devices. 3C-SiC is the only polytype with a cubic structure and has superior physical properties over other common SiC polytypes, such as high hole/electron mobility and low interface trap density with oxide. Due to lack of commercial native substrates, 3C-SiC is mainly grown on the cheap silicon (Si) substrates. However, there’s a large mismatch in both lattice constants and thermal expansion coefficients leading to a high density of defects in the epitaxial layers. In paper 1, the new CVD solution for growing high quality double-position-boundaries free 3C-SiC using on-axis 4H-SiC substrates is presented. Reproducible growth parameters, including temperature, C/Si ratio, ramp-up condition, Si/H2 ratio, N2 addition and pressure, are covered in this study. GaN is another attractive wide band gap semiconductor for power devices and optoelectronic applications. In the GaN-based transistors, carbon is often exploited to dope the buffer layer to be semi-insulating in order to isolate the device active region from the substrate. The conventional way is to use the carbon atoms on the gallium precursor and control the incorporation by tuning the process parameters, e.g. temperature, pressure. However, there’s a risk of obtaining bad morphology and thickness uniformity if the CVD process is not operated in an optimal condition. In addition, carbon source from the graphite insulation and improper coated graphite susceptor may also contribute to the doping in a CVD reactor, which is very difficult to be controlled in a reproducible way. Therefore, in paper 2, intentional carbon doping of (0001) GaN using six hydrocarbon precursors, i.e. methane (CH4), ethylene (C2H4), acetylene (C2H2), propane (C3H8), iso-butane (i-C4H10) and trimethylamine (N(CH3)3), have been explored. In paper 3, propane is chosen for carbon doping when growing the high electron mobility transistor (HEMT) structure on a quarter of 3-inch 4H-SiC wafer. The quality of epitaxial layer and fabricated devices is evaluated. In paper 4, the behaviour of carbon doping using carbon atoms from the gallium precursor, trimethylgallium (Ga(CH3)3), is explained by thermochemical and quantum chemical modelling and compared with the experimental results. GaN is commonly grown on foreign substrates, such as sapphire (Al2O3), Si and SiC, resulting in high stress and high threading dislocation densities. Hence, bulk GaN substrates are preferred for epitaxy. In paper 5, the morphological, structural and luminescence properties of GaN epitaxial layers grown on N-face free-standing GaN substrates are studied since the N-face GaN has advantageous characteristics compared to the Ga...

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Optimization of low temperature GaN buffer layers for halide vapor phase epitaxy growth of bulk GaN

Cited by 28 publications

References 30 publications

Dislocation related droop in InGaN/GaN light emitting diodes investigated via cathodoluminescence

Dislocation related droop in InGaN/GaN light emitting diodes investigated via cathodoluminescence

Optical properties of C-doped bulk GaN wafers grown by halide vapor phase epitaxy

CVD solutions for new directions in SiC and GaN epitaxy

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