Study of defects in LED epitaxial layers grown on the optimized hemispherical patterned sapphire substrates

Zhou, Shunhua; Wang, Haiyan; Lin, Zhien; Yang, Hui; Hong, Xiaosong; Li, Guoqiang

doi:10.7567/jjap.53.025503

Cited by 21 publications

(16 citation statements)

References 54 publications

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“…Because we use lower RF plasma radical generator power of 500 W during the initial growth, the interfacial reactions between N plasmas produced by RF plasma radical generator and O atoms diffused from the substrates can be suppressed, and eventually results in the higher crystalline quality of GaN. Additionally, it is known that the FWHM of GaN(0002) is related to the skew dislocation that is formed by the various height of substrates, and the FWHM of GaN(10-12) is respected to the pure edge and mixed dislocations which are generated during the coalescence process among the mis-oriented individual islands242526. The skew dislocation density, and pure edge and mixed dislocation densities in as-grown GaN epi-layer are estimated to be 7.9 × 10 7 , and 8.8 × 10 7 cm −2 , respectively2728.…”

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confidence: 99%

Highly-efficient GaN-based light-emitting diode wafers on La0.3Sr1.7AlTaO6 substrates

Wang

Yang

Gao

et al. 2015

Sci Rep

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Highly-efficient GaN-based light-emitting diode (LED) wafers have been grown on La0.3Sr1.7AlTaO6 (LSAT) substrates by radio-frequency molecular beam epitaxy (RF-MBE) with optimized growth conditions. The structural properties, surface morphologies, and optoelectronic properties of as-prepared GaN-based LED wafers on LSAT substrates have been characterized in detail. The characterizations have revealed that the full-width at half-maximums (FWHMs) for X-ray rocking curves of GaN(0002) and GaN(10-12) are 190.1 and 210.2 arcsec, respectively, indicating that high crystalline quality GaN films have been obtained. The scanning electron microscopy and atomic force microscopy measurements have shown the very smooth p-GaN surface with the surface root-mean-square (RMS) roughness of 1.3 nm. The measurements of low-temperature and room-temperature photoluminescence help to calculate the internal quantum efficiency of 79.0%. The as-grown GaN-based LED wafers have been made into LED chips with the size of 300 × 300 μm2 by the standard process. The forward voltage, the light output power and the external quantum efficiency for LED chips are 19.6 W, 2.78 V, and 40.2%, respectively, at a current of 20 mA. These results reveal the high optoelectronic properties of GaN-based LEDs on LSAT substrates. This work brings up a broad future application of GaN-based devices.

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confidence: 99%

Highly-efficient GaN-based light-emitting diode wafers on La0.3Sr1.7AlTaO6 substrates

Wang

Yang

Gao

et al. 2015

Sci Rep

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“…The SAG of arsenide and phosphide III-V materials has been analyzed quite extensively and utilized as a major method for nanowire growth [52][53][54]. In III-N technology, SAG has been employed mostly in epitaxial lateral overgrowth (ELOG) methods which were developed to reduce threading dislocations in heteroepitaxial growth [55][56][57]. In contrast with ion implantation, the extensively characterized [58][59][60][61][62] defect-free GaN layers grown by lateral epitaxial over-growth can provide a more beneficial solution to realize LHJ structures [63].…”

Section: Selective Area Growth As a Methods To Realize A Lateral Pn-jumentioning

confidence: 99%

Diffusion-Driven Charge Transport in Light Emitting Devices

Kim¹,

Kivisaari²,

Oksanen³

et al. 2017

Preprint

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Almost all modern inorganic light-emitting diode (LED) designs are based on double heterojunctions (DHJs) whose structure and current injection principle have remained essentially unchanged for decades. Although highly efficient devices based on the DHJ design have been developed and commercialized for energy-efficient general lighting, the conventional DHJ design requires burying the active region (AR) inside a pn-junction. This has hindered the development of emitters utilizing nanostructured ARs located close to device surfaces such as nanowires or surface quantum wells. Modern DHJ III-N LEDs also exhibit resistive losses which arise from the DHJ device geometry. The recently introduced diffusion-driven charge transport (DDCT) emitter design offers a novel way to transport charge carriers to unconventionally placed ARs. In a DDCT device, the AR is located apart from the pn-junction and the charge carriers are injected into the AR by bipolar diffusion. This device design allows the integration of surface ARs to semiconductor LEDs and offers a promising method to reduce resistive losses in high power devices. In this work, we present a review of the recent progress in gallium nitride (GaN) based DDCT devices, and an outlook of potential DDCT has for opto-and microelectronics.

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“…The variations of crystal improvement techniques has been attempted for GaN on LT buffer, including pendeoepitaxy [93] and facet-controlled ELO [94], which involve the masking of dislocations and utilizing the mass transfer of GaN. In addition, the use of a PSS gives a TDD on the order of 10 8 /cm 2 [95,96]; PSS technique utilizes the decomposition of irregularly oriented GaN seed crystals on sapphire. GaN substrates with TDD of lower than 10 6 /cm 2 are currently used for the production of LDs, and ELO-GaN has been replaced by GaN substrates [97,98] to produce LDs.…”

Section: Epitaxial Lateral Overgrowth (Elo) and Patterned Sapphire Sumentioning

confidence: 99%

A Review of AlGaN-Based Deep-Ultraviolet Light-Emitting Diodes on Sapphire

Nagasawa¹,

Hirano²

2018

Applied Sciences

185

111

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This paper reviews the progress of AlGaN-based deep-ultraviolet (DUV) light emitting diodes (LEDs), mainly focusing in the work of the authors’ group. The background to the development of the current device structure on sapphire is described and the reason for using a (0001) sapphire with a miscut angle of 1.0° relative to the m-axis is clarified. Our LEDs incorporate uneven quantum wells (QWs) grown on an AlN template with dense macrosteps. Due to the low threading dislocation density of AlGaN and AlN templates of about 5 × 108/cm2, the number of nonradiative recombination centers is decreased. In addition, the uneven QW show high external quantum efficiency (EQE) and wall-plug efficiency, which are considered to be boosted by the increased internal quantum efficiency (IQE) by enhancing carrier localization adjacent to macrosteps. The achieved LED performance is considered to be sufficient for practical applications. The advantage of the uneven QW is discussed in terms of the EQE and IQE. A DUV-LED die with an output of over 100 mW at 280–300 nm is considered feasible by applying techniques including the encapsulation. In addition, the fundamental achievements of various groups are reviewed for the future improvements of AlGaN-based DUV-LEDs. Finally, the applications of DUV-LEDs are described from an industrial viewpoint. The demonstrations of W/cm2-class irradiation modules are shown for UV curing.

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Study of defects in LED epitaxial layers grown on the optimized hemispherical patterned sapphire substrates

Cited by 21 publications

References 54 publications

Highly-efficient GaN-based light-emitting diode wafers on La0.3Sr1.7AlTaO6 substrates

Highly-efficient GaN-based light-emitting diode wafers on La0.3Sr1.7AlTaO6 substrates

Diffusion-Driven Charge Transport in Light Emitting Devices

A Review of AlGaN-Based Deep-Ultraviolet Light-Emitting Diodes on Sapphire

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