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Ultralow threading dislocation density in GaN epilayer on near-strain-free GaN compliant buffer layer and its applications in hetero-epitaxial LEDs.

Shih HY, Shiojiri M, Chen CH, Yu SF, Ko CT, Yang JR, Lin RM, Chen MJ - Sci Rep (2015)

Bottom Line: Here, we report InGaN/GaN LEDs with ultralow TD density and improved efficiency on a sapphire substrate, on which a near strain-free GaN compliant buffer layer was grown by remote plasma atomic layer deposition.This "compliant" buffer layer is capable of relaxing strain due to the absorption of misfit dislocations in a region within ~10 nm from the interface, leading to a high-quality overlying GaN epilayer with an unusual TD density as low as 2.2 × 10(5) cm(-2).In addition, this GaN compliant buffer layer exhibits excellent uniformity up to a 6" wafer, revealing a promising means to realize large-area GaN hetero-epitaxy for efficient LEDs and high-power transistors.

View Article: PubMed Central - PubMed

Affiliation: Department of Materials Science and Engineering, National Taiwan University, Taipei, Taiwan.

ABSTRACT
High threading dislocation (TD) density in GaN-based devices is a long unresolved problem because of the large lattice mismatch between GaN and the substrate, which causes a major obstacle for the further improvement of next-generation high-efficiency solid-state lighting and high-power electronics. Here, we report InGaN/GaN LEDs with ultralow TD density and improved efficiency on a sapphire substrate, on which a near strain-free GaN compliant buffer layer was grown by remote plasma atomic layer deposition. This "compliant" buffer layer is capable of relaxing strain due to the absorption of misfit dislocations in a region within ~10 nm from the interface, leading to a high-quality overlying GaN epilayer with an unusual TD density as low as 2.2 × 10(5) cm(-2). In addition, this GaN compliant buffer layer exhibits excellent uniformity up to a 6" wafer, revealing a promising means to realize large-area GaN hetero-epitaxy for efficient LEDs and high-power transistors.

No MeSH data available.


Related in: MedlinePlus

Characteristics of the ALD GaN buffer layer.(a) XRD patterns of the as-deposited and PDA-treated GaN BLs grown by RP-ALD together with that of the PDA-treated GaN NL grown by MOCVD. (b) Room-temperature micro-PL spectra of the PDA-treated ALD BL and the PDA-treated MOCVD NL. The magnified PL spectra are shown in the inset.
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f1: Characteristics of the ALD GaN buffer layer.(a) XRD patterns of the as-deposited and PDA-treated GaN BLs grown by RP-ALD together with that of the PDA-treated GaN NL grown by MOCVD. (b) Room-temperature micro-PL spectra of the PDA-treated ALD BL and the PDA-treated MOCVD NL. The magnified PL spectra are shown in the inset.

Mentions: The X-ray diffraction (XRD) patterns of as-deposited and PDA-treated GaN BLs grown by RP-ALD are shown in Fig. 1(a), with a comparison to the PDA-treated GaN NL grown by MOCVD. Significant reflection at 34.6° is associated with the hexagonal GaN (0002), indicating that both the as-deposited and PDA-treated GaN BLs were crystallized with a wurtzite structure. The remarkable enhancement of the XRD peak intensity (green and blue lines) reveals that the PDA treatment greatly improves the crystallinity of the GaN BL grown by RP-ALD. Accordingly, it can be deduced that the as-deposited GaN is composed of fine grains and thus exhibits the diffuse XRD peak. During the PDA treatment, the fine grains grew by recrystallization and coalescence and with each other, resulting in a nearly perfect single crystal exhibiting the strong (0002) reflection peak in the XRD pattern. Notably, the XRD peak intensity and full width at half maximum (FWHM) of the PDA-treated ALD BL are superior to those of the PDA-treated MOCVD NL, indicating better crystal quality in the GaN layer grown by RP-ALD. The room-temperature micro-photoluminescence (PL) spectra of the PDA-treated ALD BL and the PDA-treated MOCVD NL are shown in Fig. 1(b). The near-band-edge PL intensity at 364 nm of the ALD BL is significantly higher than that of the MOCVD NL, and the defect-related band at approximately 550 nm is much weaker, which also indicates the superior crystal quality of the ALD BL.


Ultralow threading dislocation density in GaN epilayer on near-strain-free GaN compliant buffer layer and its applications in hetero-epitaxial LEDs.

Shih HY, Shiojiri M, Chen CH, Yu SF, Ko CT, Yang JR, Lin RM, Chen MJ - Sci Rep (2015)

Characteristics of the ALD GaN buffer layer.(a) XRD patterns of the as-deposited and PDA-treated GaN BLs grown by RP-ALD together with that of the PDA-treated GaN NL grown by MOCVD. (b) Room-temperature micro-PL spectra of the PDA-treated ALD BL and the PDA-treated MOCVD NL. The magnified PL spectra are shown in the inset.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4556983&req=5

f1: Characteristics of the ALD GaN buffer layer.(a) XRD patterns of the as-deposited and PDA-treated GaN BLs grown by RP-ALD together with that of the PDA-treated GaN NL grown by MOCVD. (b) Room-temperature micro-PL spectra of the PDA-treated ALD BL and the PDA-treated MOCVD NL. The magnified PL spectra are shown in the inset.
Mentions: The X-ray diffraction (XRD) patterns of as-deposited and PDA-treated GaN BLs grown by RP-ALD are shown in Fig. 1(a), with a comparison to the PDA-treated GaN NL grown by MOCVD. Significant reflection at 34.6° is associated with the hexagonal GaN (0002), indicating that both the as-deposited and PDA-treated GaN BLs were crystallized with a wurtzite structure. The remarkable enhancement of the XRD peak intensity (green and blue lines) reveals that the PDA treatment greatly improves the crystallinity of the GaN BL grown by RP-ALD. Accordingly, it can be deduced that the as-deposited GaN is composed of fine grains and thus exhibits the diffuse XRD peak. During the PDA treatment, the fine grains grew by recrystallization and coalescence and with each other, resulting in a nearly perfect single crystal exhibiting the strong (0002) reflection peak in the XRD pattern. Notably, the XRD peak intensity and full width at half maximum (FWHM) of the PDA-treated ALD BL are superior to those of the PDA-treated MOCVD NL, indicating better crystal quality in the GaN layer grown by RP-ALD. The room-temperature micro-photoluminescence (PL) spectra of the PDA-treated ALD BL and the PDA-treated MOCVD NL are shown in Fig. 1(b). The near-band-edge PL intensity at 364 nm of the ALD BL is significantly higher than that of the MOCVD NL, and the defect-related band at approximately 550 nm is much weaker, which also indicates the superior crystal quality of the ALD BL.

Bottom Line: Here, we report InGaN/GaN LEDs with ultralow TD density and improved efficiency on a sapphire substrate, on which a near strain-free GaN compliant buffer layer was grown by remote plasma atomic layer deposition.This "compliant" buffer layer is capable of relaxing strain due to the absorption of misfit dislocations in a region within ~10 nm from the interface, leading to a high-quality overlying GaN epilayer with an unusual TD density as low as 2.2 × 10(5) cm(-2).In addition, this GaN compliant buffer layer exhibits excellent uniformity up to a 6" wafer, revealing a promising means to realize large-area GaN hetero-epitaxy for efficient LEDs and high-power transistors.

View Article: PubMed Central - PubMed

Affiliation: Department of Materials Science and Engineering, National Taiwan University, Taipei, Taiwan.

ABSTRACT
High threading dislocation (TD) density in GaN-based devices is a long unresolved problem because of the large lattice mismatch between GaN and the substrate, which causes a major obstacle for the further improvement of next-generation high-efficiency solid-state lighting and high-power electronics. Here, we report InGaN/GaN LEDs with ultralow TD density and improved efficiency on a sapphire substrate, on which a near strain-free GaN compliant buffer layer was grown by remote plasma atomic layer deposition. This "compliant" buffer layer is capable of relaxing strain due to the absorption of misfit dislocations in a region within ~10 nm from the interface, leading to a high-quality overlying GaN epilayer with an unusual TD density as low as 2.2 × 10(5) cm(-2). In addition, this GaN compliant buffer layer exhibits excellent uniformity up to a 6" wafer, revealing a promising means to realize large-area GaN hetero-epitaxy for efficient LEDs and high-power transistors.

No MeSH data available.


Related in: MedlinePlus