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Influence of patterned sapphire substrates with different symmetry on the light output power of InGaN-based LEDs.

You YH, Su VC, Ho TE, Lin BW, Lee ML, Das A, Hsu WC, Kuan CH, Lin RM - Nanoscale Res Lett (2014)

Bottom Line: The GaN epitaxial layers grown on the hexagonal lattice arrangement PSS (HLAPSS) have a lower compressive strain than the ones grown on the square lattice arrangement PSS (SLAPSS).The quantum-confined Stark effect (QCSE) is also affected by the residual compressive strain.Based on the experimentally measured data and the ray tracing simulation results, the InGaN-based LED with the HLAPSS has a higher LOP than the one with the SLAPSS due to the weaker QCSE within multiple-quantum wells (MQWs).

View Article: PubMed Central - HTML - PubMed

Affiliation: Graduate Institute of Electronic Engineering and Department of Electrical Engineering, National Taiwan University, No. 1, Roosevelt Road Section 4, Daan District, Taipei 10617, Taiwan.

ABSTRACT
This paper aims to investigate the light output power (LOP) of InGaN-based light-emitting diodes (LEDs) grown on patterned sapphire substrates (PSSs) with different symmetry. The GaN epitaxial layers grown on the hexagonal lattice arrangement PSS (HLAPSS) have a lower compressive strain than the ones grown on the square lattice arrangement PSS (SLAPSS). The quantum-confined Stark effect (QCSE) is also affected by the residual compressive strain. Based on the experimentally measured data and the ray tracing simulation results, the InGaN-based LED with the HLAPSS has a higher LOP than the one with the SLAPSS due to the weaker QCSE within multiple-quantum wells (MQWs).

No MeSH data available.


Related in: MedlinePlus

Raman results for the InGaN-based LEDs on the CSS and PSSs. (a) The room temperature Raman spectra and (b) the corresponding room temperature Raman shift and Raman line width.
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Figure 2: Raman results for the InGaN-based LEDs on the CSS and PSSs. (a) The room temperature Raman spectra and (b) the corresponding room temperature Raman shift and Raman line width.

Mentions: To gain insight into the correlation between the PSSs with different symmetry and the strain variation in the GaN epitaxial layers, the micro-Raman measurement is required. Figure 2a shows the room temperature Raman spectra, and Figure 2b indicates the associated Raman shift and line width of GaN E2(high) mode of the InGaN-based LEDs having the CSS, SLAPSS, and HLAPSS. The Raman shifts of the E2(high) mode of InGaN-based LEDs grown on the CSS, SLAPSS, and HLAPSS are 569.11, 569.08, and 568.82 cm-1, respectively. Since the literature[21] demonstrated that the E2(high) phonon frequency of a perfect GaN is 567.6 cm-1 at room temperature measurement and the residual compressive strain can be calculated through the measured E2(high) mode Raman shift[22], the associated residual compressive strain is calculated to be -1.22 × 10-3 for the InGaN-based LEDs grown on the CSS. The other calculated values of the residual compressive strain are -1.21 × 10-3 and -1.07 × 10-3 for the InGaN-based LEDs having the SLAPSS and HLAPSS, respectively. This reveals that the InGaN-based LED grown on the HLAPSS has the lowest residual compressive strain. The smallest Raman line width of the sample with HLAPSS is also shown in the figure. These results may imply that the growths of InGaN-based LED on the HLAPSS can improve the bulk GaN crystalline quality through the relaxation of the residual compressive strain as a result of the higher symmetry of HLAPSS.


Influence of patterned sapphire substrates with different symmetry on the light output power of InGaN-based LEDs.

You YH, Su VC, Ho TE, Lin BW, Lee ML, Das A, Hsu WC, Kuan CH, Lin RM - Nanoscale Res Lett (2014)

Raman results for the InGaN-based LEDs on the CSS and PSSs. (a) The room temperature Raman spectra and (b) the corresponding room temperature Raman shift and Raman line width.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4225452&req=5

Figure 2: Raman results for the InGaN-based LEDs on the CSS and PSSs. (a) The room temperature Raman spectra and (b) the corresponding room temperature Raman shift and Raman line width.
Mentions: To gain insight into the correlation between the PSSs with different symmetry and the strain variation in the GaN epitaxial layers, the micro-Raman measurement is required. Figure 2a shows the room temperature Raman spectra, and Figure 2b indicates the associated Raman shift and line width of GaN E2(high) mode of the InGaN-based LEDs having the CSS, SLAPSS, and HLAPSS. The Raman shifts of the E2(high) mode of InGaN-based LEDs grown on the CSS, SLAPSS, and HLAPSS are 569.11, 569.08, and 568.82 cm-1, respectively. Since the literature[21] demonstrated that the E2(high) phonon frequency of a perfect GaN is 567.6 cm-1 at room temperature measurement and the residual compressive strain can be calculated through the measured E2(high) mode Raman shift[22], the associated residual compressive strain is calculated to be -1.22 × 10-3 for the InGaN-based LEDs grown on the CSS. The other calculated values of the residual compressive strain are -1.21 × 10-3 and -1.07 × 10-3 for the InGaN-based LEDs having the SLAPSS and HLAPSS, respectively. This reveals that the InGaN-based LED grown on the HLAPSS has the lowest residual compressive strain. The smallest Raman line width of the sample with HLAPSS is also shown in the figure. These results may imply that the growths of InGaN-based LED on the HLAPSS can improve the bulk GaN crystalline quality through the relaxation of the residual compressive strain as a result of the higher symmetry of HLAPSS.

Bottom Line: The GaN epitaxial layers grown on the hexagonal lattice arrangement PSS (HLAPSS) have a lower compressive strain than the ones grown on the square lattice arrangement PSS (SLAPSS).The quantum-confined Stark effect (QCSE) is also affected by the residual compressive strain.Based on the experimentally measured data and the ray tracing simulation results, the InGaN-based LED with the HLAPSS has a higher LOP than the one with the SLAPSS due to the weaker QCSE within multiple-quantum wells (MQWs).

View Article: PubMed Central - HTML - PubMed

Affiliation: Graduate Institute of Electronic Engineering and Department of Electrical Engineering, National Taiwan University, No. 1, Roosevelt Road Section 4, Daan District, Taipei 10617, Taiwan.

ABSTRACT
This paper aims to investigate the light output power (LOP) of InGaN-based light-emitting diodes (LEDs) grown on patterned sapphire substrates (PSSs) with different symmetry. The GaN epitaxial layers grown on the hexagonal lattice arrangement PSS (HLAPSS) have a lower compressive strain than the ones grown on the square lattice arrangement PSS (SLAPSS). The quantum-confined Stark effect (QCSE) is also affected by the residual compressive strain. Based on the experimentally measured data and the ray tracing simulation results, the InGaN-based LED with the HLAPSS has a higher LOP than the one with the SLAPSS due to the weaker QCSE within multiple-quantum wells (MQWs).

No MeSH data available.


Related in: MedlinePlus