Optical absorption sensing with dual-spectrum silicon LEDs in SOI-CMOS technology

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Abstract

Silicon p-n junction diodes emit low-intensity, broad-spectrum light near 1120 nm in forward bias and between 400-900 nm in reverse bias (avalanche). For the first time, we experimentally achieve optical absorption sensing of pigment in solution with silicon micro LEDs designed in a standard silicon-on-insulator CMOS technology. By driving a single LED in both forward and avalanche modes of operation, we steer it's electroluminescent spectrum between visible and near-infrared (NIR). We then characterize the vertical optical transmission of both visible and NIR light from the LED through the same micro-droplet specimen to a vertically mounted discrete silicon photodiode. The effective absorption coefficient of carmine solution in glycerol at varying concentrations were extracted from the color ratio in optical coupling. By computing the LED-specific molar absorption coefficient of carmine, we estimate the concentration (∼0.040 mol L-1) and validate the same with a commercial spectrophotometer (∼0.030 mol L-1). With a maximum observed sensitivity of ∼1260 cm-1mol-1L, the sensor is a significant step forward towards low-cost CMOS-integrated optical sensors with silicon LED as the light source intended for biochemical analyses in food sector and plant/human health.

Original languageEnglish
Title of host publicationProceedings IEEE Sensors, SENSORS 2020
Place of PublicationPiscataway, NJ, USA
PublisherIEEE
Number of pages4
ISBN (Electronic)978-1-7281-6801-2
DOIs
Publication statusPublished - 2020
Event2020 IEEE Sensors, SENSORS 2020 - Virtual, Rotterdam, Netherlands
Duration: 25 Oct 202028 Oct 2020

Conference

Conference2020 IEEE Sensors, SENSORS 2020
CountryNetherlands
CityVirtual, Rotterdam
Period25/10/2028/10/20

Keywords

  • Avalanche breakdown
  • CMOS
  • light-emitting diode
  • Optical sensing
  • Silicon

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