2015
DOI: 10.1038/lsa.2015.36
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Overcoming the fundamental light-extraction efficiency limitations of deep ultraviolet light-emitting diodes by utilizing transverse-magnetic-dominant emission

Abstract: 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 thr… Show more

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Cited by 121 publications
(63 citation statements)
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“…Sidewall emission-enhanced (SEE) DUV LEDs with multiple light-emitting mesa stripes and three-dimensional reflectors between the stripes have been explored to enhance the light extraction efficiency of TM polarized light. [21,22] Remarkably enhanced light extraction 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 has been observed in the SEE DUV LEDs with an emission wavelength of 285 nm. The devices also showed reduced operating voltage due to improved n-type ohmic contacts formed on the regrown n-GaN stripes compared with conventional LEDs.…”
Section: Device Design For Improved Performance Of Group Iii-nitrde Dmentioning
confidence: 98%
“…Sidewall emission-enhanced (SEE) DUV LEDs with multiple light-emitting mesa stripes and three-dimensional reflectors between the stripes have been explored to enhance the light extraction efficiency of TM polarized light. [21,22] Remarkably enhanced light extraction 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 has been observed in the SEE DUV LEDs with an emission wavelength of 285 nm. The devices also showed reduced operating voltage due to improved n-type ohmic contacts formed on the regrown n-GaN stripes compared with conventional LEDs.…”
Section: Device Design For Improved Performance Of Group Iii-nitrde Dmentioning
confidence: 98%
“…Meanwhile, the top-most valence band of c-plane AlN is a crystal-field split-off hole band, as shown in Figure 9b, therefore, the light emission from AlN can be approximated as the emission from a dipole along the z-axis, which results in a strong anisotropic emission, as shown in Figure 9d. 146,147 Consequently, high-Al-content AlGaN has a similar valence band structure to AlN, therefore, it emits light propagating mainly along the in-plane direction of the active region, causing the light to be lost inside the LED chip. This explains why typical LEE-enhancing techniques are very effective for GaInN-based visible LEDs but much less effective for AlGaN DUV LEDs because those techniques favor the extraction of isotropic light emission.…”
Section: Absorption and Trapping: Light Extraction Efficiencymentioning
confidence: 99%
“…The LEDs with the nanoimprinted AlN nanophotonic structures exhibited wider near-field emitting areas, stronger farfield extracted light intensities, and an approximately 20-fold increase in the output power when DUV LEDs generally employ flip-chip configuration for efficient heat dissipation and light extraction [21][22][23][24]. In spite of this, flip-chip designs still suffer from a relatively low extraction efficiency caused by the dominant transverse magnetic (TM)-polarized light emission, which propagates mainly in the lateral direction [25]. Sidewall emission-enhanced (SEE) DUV LEDs with multiple light-emitting mesa stripes and three-dimensional reflectors between the stripes were explored to enhance the light extraction efficiency of TM-polarized light [25,26].…”
Section: Device Design For Improved Performance Of Group Iii-nitride mentioning
confidence: 99%
“…In spite of this, flip-chip designs still suffer from a relatively low extraction efficiency caused by the dominant transverse magnetic (TM)-polarized light emission, which propagates mainly in the lateral direction [25]. Sidewall emission-enhanced (SEE) DUV LEDs with multiple light-emitting mesa stripes and three-dimensional reflectors between the stripes were explored to enhance the light extraction efficiency of TM-polarized light [25,26].…”
Section: Device Design For Improved Performance Of Group Iii-nitride mentioning
confidence: 99%