Preparation of Freestanding GaN Wafers by Hydride Vapor Phase Epitaxy with Void-Assisted Separation

Oshima, Yuki; Eri, Takeshi; Shibata, Masatomo; Sunakawa, Hajime; Kobayashi, Kenji; Ichihashi, Toshinari; Usui, Akira

doi:10.1143/jjap.42.l1

Cited by 272 publications

(213 citation statements)

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“…Most of the GaN layers were grown on our standard 2-in.-diameter freestanding n-type (n = 1 × 10 18 cm −3 ) GaN substrates, produced by the void-assisted separation (VAS)-method, 16) unless otherwise noted. Results for the growth of a GaN template on a 6-in.…”

Section: Experimental Methodsmentioning

confidence: 99%

“…The development of freestanding GaN substrates with a low threading dislocation density (TDD) by several groups, including ours, [16][17][18][19][20][21][22][23][24][25][26] has markedly changed this situation, and researches on GaN-based power devices using such substrates are now accelerating. 4,5,[27][28][29] Among the various methods for the growth of freestanding GaN substrates, hydride-vaporphase epitaxy (HVPE) is the most well established, and wafers with diameters of 2-in.…”

Section: Introductionmentioning

confidence: 99%

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Hydride-vapor-phase epitaxial growth of highly pure GaN layers with smooth as-grown surfaces on freestanding GaN substrates

Fujikura

Konno

Yoshida

et al. 2017

Jpn. J. Appl. Phys.

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Thick (20–30 µm) layers of highly pure GaN with device-quality smooth as-grown surfaces were prepared on freestanding GaN substrates by using our advanced hydride-vapor-phase epitaxy (HVPE) system. Removal of quartz parts from the HVPE system markedly reduced concentrations of residual impurities to below the limits of detection by secondary-ion mass spectrometry. Appropriate gas-flow management in the HVPE system realized device-quality, smooth, as-grown surfaces with an excellent uniformity of thickness. The undoped GaN layer showed insulating properties. By Si doping, the electron concentration could be controlled over a wide range, down to 2 × 1014 cm−3, with a maximum mobility of 1150 cm2·V−1·s−1. The concentration of residual deep levels in lightly Si-doped layers was in the 1014 cm−3 range or less throughout the entire 2-in. wafer surface. These achievements clearly demonstrate the potential of HVPE as a tool for epitaxial growth of power-device structures.

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Section: Experimental Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Hydride-vapor-phase epitaxial growth of highly pure GaN layers with smooth as-grown surfaces on freestanding GaN substrates

Fujikura

Konno

Yoshida

et al. 2017

Jpn. J. Appl. Phys.

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“…31 We then investigated the correlation between the structural properties and the optical properties. Optical properties of GaN porous samples were characterized by photoluminescence (PL) and photoreflectance measurements.…”

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confidence: 99%

Correlation between Structural and Photoelectrochemical Properties of GaN Porous Nanostructures Formed by Photo-Assisted Electrochemical Etching

Kumazaki¹,

Watanabe²,

Yatabe³

et al. 2014

J. Electrochem. Soc.

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We investigated the correlation between structural and photoelectrochemical properties of GaN porous nanostructures formed by photo-assisted electrochemical etching. The porous nanostructures were formed during light irradiation of the top-surface of homo-epitaxial layers grown on freestanding GaN substrates. The pore depth, wall thickness, and surface morphology of porous nanostructures were strongly influenced by the way holes generated by the light irradiation were supplied. Such structural features influenced the optical properties of GaN porous nanostructures. The photoluminescence peaks measured on GaN porous nanostructures were shifted to higher energies because of the quantum confinement in the thin GaN walls between pores. Formation of porous nanostructure decreased the photoreflectance of the GaN surface, and the smallest reflectance was obtained from the porous sample having large pores on its surface after the ultrathin layer with small pores had been removed by surface-etching. The photoelectrochemical response measured on GaN porous nanostructures in a NaCl electrolyte were drastically enhanced by the unique features of those structures, such as low photoreflectance and large surface area. The largest photocurrents were obtained from the sample from which H 3 PO 4 treatment had removed the ultrathin layer without thinning the pore walls. Photoelectrochemical systems based on semiconductor photoelectrodes have recently attracted much attention due to their potential use in the next generation of green technologies such as water splitting for fuel cells, artificial photosynthesis, and so on.1-5 Among the photoelectrode materials, GaN is one of the most attractive because of its chemical stability and its potential to achieve direct photoelectrolysis by solar power without the consumption of electric power. [6][7][8] In addition, the bandgap energy of GaN-based materials can be varied from about 0.65 to 6.0 eV by alloying them with InN and AlN, which enables us to design various functional photoelectrodes not only for spectral matching of solar light but also for the electrochemical reduction of CO 2 to carbohydrate. 9 One of the common approaches to improving conversion efficiency is to form nanostructures on the photoelectrode surface in order to increase its surface area. Most reported GaN nanostructures have been made using selective-area growth 10,11 or a dry etching process such as reactive ion etching. 12,13 There are, however, severe limitations on increasing the density of nanostructures because most approaches use lithography for defining the size and position of the nanostructures. And when a dry etching process is involved, the etching damage induced by ion bombardment is not negligible [14][15][16] and could significantly degrade the photoelectrochemical efficiency.One alternative approach is an electrochemical-fabrication process, which can form various semiconductor nanostructures in a self-assembled fashion. The most well-known application of an electrochemical process is the formation...

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“…This technique has been used in both metal organic chemical vapor deposition (MOCVD) [15,16] and HVPE [17]. Using this technique, it has been shown that for thicker GaN layers (> 600 µm) the bulk GaN layer is spontaneously separated from the substrate which means that many time-consuming or complicated process steps such as mechanical lapping of sapphire [18], chemical etching [19], laser lift-off [20], ELOG [21,22] and void assisted separation [23] can be avoided. Thus, there are several advantages using LT-GaN buffers since the number of process steps, and hence, the manufacturing cost can be reduced.…”

Section: Introductionmentioning

confidence: 99%

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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Preparation of Freestanding GaN Wafers by Hydride Vapor Phase Epitaxy with Void-Assisted Separation

Cited by 272 publications

References 15 publications

Hydride-vapor-phase epitaxial growth of highly pure GaN layers with smooth as-grown surfaces on freestanding GaN substrates

Hydride-vapor-phase epitaxial growth of highly pure GaN layers with smooth as-grown surfaces on freestanding GaN substrates

Correlation between Structural and Photoelectrochemical Properties of GaN Porous Nanostructures Formed by Photo-Assisted Electrochemical Etching

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

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