Growth and characterization of freestanding GaN substrates

Motoki, Kensaku; Okahisa, Takuji; Nakahata, Seiji; Matsumoto, Naoki; Kimura, Hiroya; Kasai, Hitoshi; Takemoto, Kikurou; Uematsu, Koji; Ueno, Masaki; Kumagai, Yoshinao; Koukitu, Akinori; Seki, Hisashi

doi:10.1016/s0022-0248(01)02078-4

Cited by 215 publications

(178 citation statements)

References 20 publications

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“…Before further discussing these results, we note that HVPE GaN bulk substrates have a domain structure as a result of spontaneous growth on both the ½0001-oriented crystals and on the semipolar f10 12g and/or f11 22g facets forming so-called hexagonal pits. 35 After polishing, this structure is usually invisible in SEM images; however, it can be clearly detected by panchromatic CL mapping (Fig. 5(b)) taken at the same spatial position as the SEM topograph illustrated in Fig.…”

Section: à3mentioning

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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Section: à3mentioning

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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“…Different approaches were used for this purpose, e.g. : direct calibration by X-ray topography [1] (suitable for dislocation density below 10 5 cm -2 ), comparison with cathodoluminescence (CL) [2], electron beam induced current (EBIC) [3] or another calibrated etching method [4], sequent etching [5] and calibration by TEM, as in e.g. [4][5][6][7][8].…”

Section: Introductionmentioning

confidence: 99%

Orthodox etching of HVPE-grown GaN

Weyher

Lazar

Macht

et al. 2007

Journal of Crystal Growth

116

103

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Orthodox etching of HVPE-grown GaN in molten eutectic of KOH + NaOH (E etch) and in hot sulfuric and phosphoric acids (HH etch) is discussed in detail. Three size grades of pits are formed by the preferential E etching at the outcrops of threading dislocations on the Ga-polar surface of GaN. Using transmission electron microscopy (TEM) as the calibration tool it is shown that the largest pits are formed on screw, intermediate on mixed and the smallest on edge dislocations. This sequence of size does not follow the sequence of the Burgers values (and thus the magnitude of the elastic energy) of corresponding dislocations. This discrepancy is explained taking into account the effect of decoration of dislocations, the degree of which is expected to be different depending on the lattice deformation around the dislocations, i.e. on the edge component of the Burgers vector. It is argued that the large scatter of optimal etching temperatures required for revealing all three types of dislocations in HVPE-grown samples from different sources also depends upon the energetic status of dislocations. The role of kinetics for reliability of etching in both etches is discussed and the way of optimization of the etching parameters is shown.

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“…A SiO 2 layer was deposited by chemical vapor deposition and then fabricated into mask/window stripes with a period of about 7 m, using conventional photolithographic techniques. Alternatives of using W [22] and SiN [44] masks instead of SiO 2 , or using GaAs [45], LiGaO 2 [46], LiAlO 2 [47] substrates instead of sapphire, have also been demonstrated. In addition, in order to further reduce the dislocation density, the ELOG approach can be performed by the socalled two-step (2S) approach, which can employ either a second layer of mask usually with shifted period with respect to the first mask or a change of the growth parameters, usually a reduced growth temperature [40].…”

Section: A Single Substrate Developmentmentioning

confidence: 99%

GaN Substrates for III-Nitride Devices

2010

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| Despite the rapid commercialization of III-nitride semiconductor devices for applications in visible and ultraviolet optoelectronics and in high-power and high-frequency electronics, their full potential is limited by two primary obstacles: i) a high defect density and biaxial strain due to the heteroepitaxial growth on foreign substrates, which result in lower performance and shortened device lifetime, and ii) a strong built-in electric field due to spontaneous and piezoelectric polarization in the wurtzite structures along the well-established [0001] growth direction for nitrides. Recent advances in the research, development, and commercial production of native GaN substrates with low defect density and high structural and optical quality have opened opportunities to overcome both of these obstacles and have led to significant progress in the development of several optoelectronic and high-power devices. In this paper, the recent achievements in bulk GaN growth development using different approaches are reviewed; comparison of the bulk materials grown in different directions is made; and the current achievements in device performance utilizing native GaN substrate material are summarized.

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Growth and characterization of freestanding GaN substrates

Cited by 215 publications

References 20 publications

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

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

Orthodox etching of HVPE-grown GaN

GaN Substrates for III-Nitride Devices

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