Intensity-Stabilized LEDs With Monolithically Integrated Photodetectors

To overcome light output degradations and fluctuations of intensities from light-emitting diodes (LEDs) over time, the monolithic integration of InGaN LEDs and photodetectors (PDs) is demonstrated in this paper. The InGaN/GaN multiquantum wells (MQWs) play the role of light emission and detection fr...

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Bibliographic Details
Published inIEEE transactions on industrial electronics (1982) Vol. 66; no. 9; pp. 7426 - 7432
Main Authors Li, Kwai Hei, Lu, Haitao, Fu, Wai Yuen, Cheung, Yuk Fai, Choi, Hoi Wai
Format Journal Article
LanguageEnglish
Published New York IEEE 01.09.2019
The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subjects
Absorption
Feedback
Feedback circuits
Gallium nitride
Gallium nitrides
Indium gallium nitrides
Light emission
Light emitting diodes
light-emitting diode (LED)
Lighting
Luminous intensity
Microcontrollers
Monitoring
monolithic integration
Organic light emitting diodes
Photoconductivity
Photodegradation
photodetector (PD)
Photodetectors
Photoelectric effect
Photoelectric emission
Photometers
Quantum well devices
Sapphire
Substrates
Variation
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Summary:To overcome light output degradations and fluctuations of intensities from light-emitting diodes (LEDs) over time, the monolithic integration of InGaN LEDs and photodetectors (PDs) is demonstrated in this paper. The InGaN/GaN multiquantum wells (MQWs) play the role of light emission and detection from the LED and PD, respectively. Despite the larger bandgap energies of the InGaN layers, the MQWs absorb light emitted by the LED due to the band tail effect, extending the absorption range up to 460 nm, which correspond to the peak wavelength of emission. The tiny-sized PD detects light from the adjacent LED coupled through the sapphire substrate to generate a photocurrent that is proportional to its light output, but remains unresponsive to ambient lighting. Apart from real-time light output monitoring, the photocurrent can be used as a feedback signal for regulation of light output. A microcontroller-based feedback circuit has been implemented to drive the LED and the photocurrent level is maintained to a preset value by adjustment of the driving current. Using this scheme, light output from the LED is stabilized to within ∼0.2% over 1-h periods.
ISSN:0278-0046
1557-9948
DOI:10.1109/TIE.2018.2873522