New developments on high-efficiency infrared and InGaAlP light-emitting diodes at OSRAM Opto Semiconductors

Broell, Markus; Sundgren, P.; Rudolph, Andreas; Schmid, W.; Vogl, Anton; Behringer, Martin

doi:10.1117/12.2039078

Cited by 29 publications

(29 citation statements)

References 2 publications

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“…The g CQE ¼ 0.70 reported here exceeds the CQE records (g CQE ¼ 0.63) we have reported previously 14,15 and also slightly exceeds the highest EQE g EQE ¼ 0.68 reported for GaAs based LEDs in the literature. 3 While directly comparing the EQE of established GaAs LEDs and our devices' CQE is not straightforward, we nevertheless point out that they both provide a lower limit for the IQE; thus, our result increases the directly measured lower bound for the IQE of GaAs based LEDs. 3 For further device optimization and better understanding of the physical processes taking place in the DDS, it is important to separately analyse the losses in the LED and the PD parts.…”

mentioning

confidence: 54%

“…3 While directly comparing the EQE of established GaAs LEDs and our devices' CQE is not straightforward, we nevertheless point out that they both provide a lower limit for the IQE; thus, our result increases the directly measured lower bound for the IQE of GaAs based LEDs. 3 For further device optimization and better understanding of the physical processes taking place in the DDS, it is important to separately analyse the losses in the LED and the PD parts. Since this is not possible through direct measurements, we estimate the magnitude of the losses using the ABC-model and the equivalent circuit described above, following the widely adopted assumptions used, e.g., for estimating and modeling the IQE of GaAs LEDs.…”

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confidence: 54%

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Thermophotonic cooling in GaAs based light emitters

Radevici

Tiira

Sadi

et al. 2019

Applied Physics Letters

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Fundamental thermodynamic considerations reveal that efficient emission from an electrically injected light emitting diode (LED) can lead to the cooling of the device. This effect, known as electroluminescent (EL) cooling, has been identified decades ago, but it has not been experimentally demonstrated in semiconductors at practical operating conditions due to the extreme requirements set for the efficiency of the light emission. To probe the conditions of EL cooling in GaAs based light emitters, we have designed and fabricated LED structures with integrated photodiodes (PDs), where the optically mediated thermal energy transport between the LED and the PD can be easily monitored. This allows characterization of the fundamental properties of the LED and a path for eliminating selected issues encountered in conventional approaches for EL cooling, such as the challenging light extraction. Despite several remaining nonidealities, our setup demonstrates a very high directly measured quantum efficiency of 70%. To characterize the bulk part of the LED, we also employ a model for estimating the power conversion efficiency (PCE) of the LED, without the contribution of non-fundamental nonidealities such as photodetection losses. Our results suggest that the PCE of the LED peaks at around 105-115%, exceeding the 100% barrier required to reach the EL cooling regime by a clear margin. This implies that the LED component in our device is in fact cooling down by transporting thermal energy carried by the emitted photons to the PD. This provides a compelling incentive for further study to confirm the result and to find ways to extend it for practically useful EL cooling.Published under license by AIP Publishing. https://doi.

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confidence: 54%

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confidence: 54%

Thermophotonic cooling in GaAs based light emitters

Radevici

Tiira

Sadi

et al. 2019

Applied Physics Letters

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“…One of the obstacles for more extensive penetration of solid‐state lighting into human life is the substantial efficiency reduction of both III‐nitride and III‐phosphide LEDs in the spectral range between 500 nm and 600 nm, which is known as the ‘green gap' problem . In the case of phosphide LEDs, the efficiency reduction is attributed to (i) suppression of radiative recombination caused by filling up the X‐valleys of the conduction band with electrons and (ii) leakage of electrons into p‐side of an LED structure over insufficiently high barriers formed in the conduction band due to low offsets.…”

Section: Introductionmentioning

confidence: 99%

Spectral dependence of light extraction efficiency of high‐power III‐nitride light‐emitting diodes

Karpov¹,

Binder

Galler

et al. 2015

Physica Rapid Research Ltrs

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Using the recently suggested method of processing the data on external quantum efficiency as a function of output optical power, we have estimated the dependence of light extraction efficiency of high‐power light‐emitting diodes (LEDs) on their emission wavelength varied between 425 nm and 540 nm. The extraction efficiency is found to increase with the wavelength from ∼80% to ∼85% in this spectral range and to correlate with the wavelength dependence of reflectivity of the large‐area p‐electrode being the essential unit of the LED chip design. The correlation found identifies the incomplete reflection of emitted light from the electrode as the major mechanism eventually controlling the spectral dependence of the efficiency of light extraction from the LEDs. Spectral dependence of light extraction efficiency of the UX:3TM LED chip: comparison of experiment and modelling results. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)

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“…The best light‐extraction efficiency for a 1 × 1 mm 2 high‐power thin‐film GaN blue LED is reported to be 80–90% . For a similar AlGaInP red LED, the reported light‐extraction efficiency is typically in the range of 30–40%, though a light‐extraction efficiency as high as ≈65% has been reported recently from a state‐of‐the‐art commercial device . Other techniques such as photonic crystals, moth‐eye structures, micro domes have also been extensively studied to further improve the light‐extraction efficiency of LEDs .…”

Section: Introductionmentioning

confidence: 99%

High‐Efficiency, High‐Power AlGaInP Thin‐Film LEDs with Micron‐Sized Truncated Cones as Light‐Extraction Structures

Wang

Kumagai

Hao

2018

Physica Status Solidi (a)

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Micron-sized truncated cones with a top surface diameter and a height on the order of the emission wavelength are prepared on the light-extraction surface of a high-power thin-film AlGaInP red LED as the light-extraction structure. An external quantum efficiency of %39.3% is obtained from a 1 Â 1 mm 2 device after resin encapsulation at an injection current of 120 mA at room temperature (%25 C). The light-extraction process in this device is investigated by means of a finite-difference time-domain (FDTD) simulation and is compared with that in a conventional AlGaInP thin-film LED with a randomly rough texture as the light-extraction structure. It is found theoretically that the extraction efficiency of light per single surface incidence of the device with the micron-sized truncated cones is a few tens of percent higher than that of a device with a randomly rough texture on the lightextraction surface. The combined effect of evanescent wave scattering at facet edges and direct extraction through some specific facets is attributed to be the main mechanism responsible for the enhancement in the lightextraction efficiency, based on the FDTD simulation.

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New developments on high-efficiency infrared and InGaAlP light-emitting diodes at OSRAM Opto Semiconductors

Cited by 29 publications

References 2 publications

Thermophotonic cooling in GaAs based light emitters

Thermophotonic cooling in GaAs based light emitters

Spectral dependence of light extraction efficiency of high‐power III‐nitride light‐emitting diodes

High‐Efficiency, High‐Power AlGaInP Thin‐Film LEDs with Micron‐Sized Truncated Cones as Light‐Extraction Structures

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