Direct observation of localized high current densities in GaN films

Brazel, E. G.; Chin, M. A.; Narayanamurti, V.

doi:10.1063/1.123853

Cited by 143 publications

(77 citation statements)

References 16 publications

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“…Fig. 7(c) ) [32][33][34] while other authors claims that this type of dislocation does not give rise to dark pits [35]. Considering the results from the XRD measurements it is tempting to draw the conclusion that the DPD is associated with screw type TD since the density of edge type TD dropped with increasing V/III-ratio.…”

Section: Gan Confirming That the Lt-gan Buffer Is Wurtzite Samples Gmentioning

confidence: 60%

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

Hemmingsson

Pozina

2013

Journal of Crystal Growth

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We have studied growth and self-separation of bulk GaN on c-oriented Al 2 O 3 using low temperature (LT) GaN buffer layers. By studying the X-ray diffraction (XRD) signature for the asymmetric and symmetric reflections versus the LT-GaN thickness and V/III precursor ratio, we observe that the peak width of the reflections is minimized using a LT buffer thickness of ~100 -300 nm. It was observed that the V/III precursor ratio has a strong influence on the morphology. In order to obtain a smooth morphology, the V/III precursor ratio has to be more than 17 during the growth of the buffer layer. By using an optimized LT buffer layer for growth of a 20 µm thick GaN layer, we obtain a XRD peak with a full width at half maximum of ~400 and ~250 arcsec for (002) and (105) reflection planes, respectively, and with a dark pit density of ~2.2 10 8 cm -2 . For layers thicker than 1 mm, the GaN was spontaneously separated and by utilizing this process, thick free freestanding 2'' GaN substrates were manufactured.

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Section: Gan Confirming That the Lt-gan Buffer Is Wurtzite Samples Gmentioning

confidence: 60%

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

Hemmingsson

Pozina

2013

Journal of Crystal Growth

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“…Screw dislocations are identified as a path of electrical conductivity so they should increase the electrical conductivity of the GaN layers [19]. Mixed dislocations are electrically inactive or not highly conductive [19][20][21]. Due to the fact that for conductive and resistive samples the number of edge defects is very similar, the ratio between screw and mixed dislocations is altered.…”

Section: Resultsmentioning

confidence: 98%

Resistivity control of unintentionally doped GaN films

Grzegorczyk¹,

Macht

Hageman

et al. 2005

phys. stat. sol. (c)

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GaN epilayers were grown on sapphire substrates via low temperature GaN and AlN nucleation layers (NL) by metalorganic chemical vapor phase epitaxy (MOCVD). The morphology of the individual NLs strongly depends on the carrier gas used during the growth and recrystallization and this is the key factor for control of the resistivity of the GaN layer grown on it. The GaN nucleation layer grown in presence of N 2 has a higher density of islands with a statistically smaller diameter than the samples grown in H 2 atmosphere. The NL grown in N 2 enables the growth GaN with a sheet resistivity higher than 3×104 Ω⋅cm as opposed to a 0.5 Ω cm value obtained for the NL grown in H 2 . Introduction of an additional intermediate (IL) low temperature (GaN or AlN) nucleation layer changes the GaN epilayer resistivity to about 50 Ω⋅cm, regardless of the carrier gas used during the growth of the IL. Defect selective etching demonstrated that control of the type and density of the dislocations in GaN enables the growth of highly resistive layers without any intentional acceptor doping (Mg, Zn). It will be demonstrated that by changing the ratio of edge type to screw dislocations the resistivity of the layer can be changed by a few orders of magnitude.

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“…This significant improvement is suggested to be originated from the suppression of leakage current due to the reduction of TDDs, which confirms with TEM results. Several types of dislocations can contribute to the reverse-bias leakage current [29], and one of the most dominant type is the screw dislocation [29]- [30]. The reduction of screw type dislocations can certainly help to reduce the reverse-bias current.…”

Section: Resultsmentioning

confidence: 99%

Improved Output Power of InGaN-Based Ultraviolet LEDs Using a Heavily Si-Doped GaN Insertion Layer Technique

Chiu

Lin

et al. 2012

IEEE J. Quantum Electron.

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Abstract-In this paper, a high quality ultraviolet lightemitting diodes (UV-LEDs) at 375 nm was developed using a heavy Si-doping technique with metal organic chemical vapor deposition. By using high-resolution X-ray diffraction, the full width at half-maximum of the rocking curve shows that the GaN film inserting a heavily Si-doped GaN layer (Si-HDL) had high crystalline quality. From the transmission electron microscopy image, the threading dislocation density was decreased after inserting a Si-HDL between undoped and n-doped GaN layers by nanoscale epitaxial lateral overgrowth. As a result, a much smaller reverse current and a higher light output were achieved. The improvement of light output at an injection current of 20 mA was enhanced by 40%. Therefore, we can use an in-situ nano pattern without complex photolithography and etching process and improve the internal quantum efficiency of UV-LEDs.Index Terms-Internal quantum efficiency, metal-organic chemical vapor deposition, nanoscale epitaxial lateral overgrowth, ultraviolet light emitting diodes.

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Direct observation of localized high current densities in GaN films

Cited by 143 publications

References 16 publications

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

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

Resistivity control of unintentionally doped GaN films

Improved Output Power of InGaN-Based Ultraviolet LEDs Using a Heavily Si-Doped GaN Insertion Layer Technique

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