Selective growth of wurtzite GaN and AlxGa1−xN on GaN/sapphire substrates by metalorganic vapor phase epitaxy

Kato, Yoshiki; Kitamura, Shota; Hiramatsu, Kazumasa; Sawaki, Nobuhiko

doi:10.1016/0022-0248(94)90448-0

Cited by 316 publications

(163 citation statements)

References 12 publications

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“…Therefore, the attempts to grow high quality crystals with low defect density [1][2][3] or to design heterostructures for carrier confinement [4,5] have been widely made. Theoretically, the optical or electric reaction can be understood as the process of electron transitions between different energy states [6].…”

Section: Introductionmentioning

confidence: 99%

Tuning linear and nonlinear optical properties of wurtzite GaN byc-axial stress

Cai¹,

Guo²

2009

J. Phys. D: Appl. Phys.

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We study the linear and nonlinear optical properties of wurtzite GaN under c-axial stress field, using density functional theory calculations. The fully structural optimization at each c-axial strain was performed. The calculated dielectric functions show that tensile c-axial strain effectively improves the linear optical efficiency, especially for the band-edge transitions, and significantly increase the mobility of electrons in the conduction band. Second-order nonlinear optical susceptibilities show that the tensile c-axial strain will enhance the zero-and low-frequency nonlinear responses of GaN. The enhancement of the nonlinear optical property is explained by the reduction of the polarization of wurtzite GaN under tensile c-axial strains. Based on these findings, we propose a method for improving the electrical and optical properties of the crystal through imposing appropriate stress on the high symmetry crystalline directions.

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Section: Introductionmentioning

confidence: 99%

Tuning linear and nonlinear optical properties of wurtzite GaN byc-axial stress

Cai¹,

Guo²

2009

J. Phys. D: Appl. Phys.

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“…The inclined facet corresponds to the 1 101 f g facet, which is generally obtained when the window mask is along 11 20 h ion the cplane. 25 The perimeter of the active stripe-patterned mesa structures, active area, and n-contact area of SEE DUV LEDs having different numbers of stripes are summarized in Table 1. Figure 5a shows the relative light output power (LOP) of the reference and SEE DUV LEDs at an injection current of 100 mA with various numbers of mesa stripes measured in the surface normal direction (on the c-axis) using a Si photodiode.…”

Section: Resultsmentioning

confidence: 99%

“…As a result of the selective area growth, three dimensional n-type GaN microstructures with isosceles trapezoidal stripes (from stripe-shaped openings) are obtained. 25 Then, the n-contact (Ti/Al/Ni/Au) is deposited on the regrown n-GaN microstructures as well as the exposed nAlGaN surface by electron-beam/thermal evaporation and annealed at 900 6 C for 2 min in ambient N 2 . The p-contact (Ni/Au) is deposited and annealed at 650 6 C for 1 min in ambient air.…”

Section: Fabrication Of See Duv Ledsmentioning

confidence: 99%

Overcoming the fundamental light-extraction efficiency limitations of deep ultraviolet light-emitting diodes by utilizing transverse-magnetic-dominant emission

et al. 2015

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While the demand for deep ultraviolet (DUV) light sources is rapidly growing, the efficiency of current AlGaN-based DUV light-emitting diodes (LEDs) remains very low due to their fundamentally limited light-extraction efficiency (LEE), calling for a novel LEE-enhancing approach to deliver a real breakthrough. Here, we propose sidewall emission-enhanced (SEE) DUV LEDs having multiple light-emitting mesa stripes to utilize inherently strong transverse-magnetic polarized light from the AlGaN active region and three-dimensional reflectors between the stripes. The SEE DUV LEDs show much enhanced light output power with a strongly upward-directed emission due to the exposed sidewall of the active region and Al-coated selective-area-grown n-type GaN micro-reflectors. The devices also show reduced operating voltage due to better n-type ohmic contact formed on the regrown n-GaN stripes when compared with conventional LEDs. Accordingly, the proposed approach simultaneously improves optical and electrical properties. In addition, strategies to further enhance the LEE up to the theoretical optimum value and control emission directionality are discussed.

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“…The SAG in MOVPE on GaN/sapphire and AlGaN/sapphire with SiO 2 stripe patterns was published for the first time in 1994 by Kato et al [5], followed by that on GaN/sapphire [6]. Intensive studies on SAG have revealed that the ELO effectively reduces the dislocation density [4,[7][8][9][10][11].…”

Section: Introductionmentioning

confidence: 99%

Hydrogen and Nitrogen Ambient Effects on Epitaxial Lateral Overgrowth (ELO) of GaN VIA Metalorganic Vapor-Phase Epitaxy (Movpe)

Tadatomo

Ohuchi

Okagawa

et al. 1999

MRS Internet j. nitride semicond. res.

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Ambient gas effect on the epitaxial lateral overgrowth (ELO) of GaN via metalorganic vapor-phase epitaxy (MOVPE) on a MOVPE-grown GaN (0001) / sapphire (0001) substrate with a SiO 2 stripe mask has been studied by means of field-emission scanning electron microscopy (SEM) and highresolution X-ray diffraction (XRD) analysis. Different ambient gases of nitrogen, hydrogen and their mixture (mixture ratio, hydrogen : nitrogen = 1 : 1) affect the lateral overgrowth rate, the surface morphology and the crystalline tilting of ELO-GaN layers. XRD revealed that the ELO-GaN layer on the SiO 2 mask aligned along the <1 -100> direction exhibited anisotropic crystalline tilting toward <11 -2 0>. For ELO-GaN growth in nitrogen ambient, the growth rate of the (0001) facet decreases, the lateral overgrowth rate increases and the tilting of the ELO-GaN layer increases, while no smooth surface is obtained, in comparison with ELO-GaN growth in hydrogen ambient. For the mixture ambient, a smooth surface with a fast lateral overgrowth rate is achieved and the dislocation density is not more than 10 7 cm -2 , which is comparable to that in hydrogen ambient. IntroductionRecently, high-performance optical devices such as light-emitting diodes (LEDs) and laser diodes (LDs) in green and ultraviolet regions have been developed using GaN, AlGaN and InGaN compound semiconductors [1,2]. These GaN-related devices are usually fabricated on a sapphire substrate, because there is no large-scale substrate for GaN heteroepitaxial growth. Due to the large differences in lattice constant, thermal expansion coefficient and chemical nature between GaN and sapphire, many threading dislocations are formed from the GaN or AlN buffer layer on the sapphire substrate, and the dislocation density has been reported to be of the order of 10 9 -10 10 cm -2 [3]. Although high-brightness LEDs have been realized in spite of the high dislocation density, the reduction of the dislocation density is desired to improve the performance and reliability of these devices. The epitaxial lateral overgrowth (ELO) technique based on the selective area growth (SAG) has recently attracted considerable attention, since the fabrication of blue-violet laser diodes on the ELO-GaN layer using this technique resulted in the achievement of a long lifetime of more than 10,000 hours [4].The SAG in MOVPE on GaN/sapphire and AlGaN/sapphire with SiO 2 stripe patterns was published for the first time in 1994 by Kato et al. [5], followed by that on GaN/sapphire [6]. Intensive studies on SAG have revealed that the ELO effectively reduces the dislocation density [4,[7][8][9][10][11]. The crystalline properties and the growth mechanism of ELO-GaN can be affected by mask patterns such as stripe direction [10][11][12][13] and growth conditions such as growth temperature [10], source gases [10], growth pressure and ambient gas. However, the effects of ambient gas remain unclear. We investigate the effects of hydrogen gas, nitrogen gas and their mixture in an atmospheric MOVPE on ELO-GaN.

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Selective growth of wurtzite GaN and AlxGa1−xN on GaN/sapphire substrates by metalorganic vapor phase epitaxy

Cited by 316 publications

References 12 publications

Tuning linear and nonlinear optical properties of wurtzite GaN byc-axial stress

Tuning linear and nonlinear optical properties of wurtzite GaN byc-axial stress

Overcoming the fundamental light-extraction efficiency limitations of deep ultraviolet light-emitting diodes by utilizing transverse-magnetic-dominant emission

Hydrogen and Nitrogen Ambient Effects on Epitaxial Lateral Overgrowth (ELO) of GaN VIA Metalorganic Vapor-Phase Epitaxy (Movpe)

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