NDIR gas sensing using high performance AllnSb mid-infrared LEDs as light source

摘要

In this paper, we report the performance of room temperature operated mid-infrared light emitting diode (LED) with an InSb buffer layer and AllnSb active/barrier layers, which showed to be suitable for non-dispersive infrared (NDIR) gas sensing. Characterization of the LED was performed and we found that good carrier confinement and crystalline quality was responsible for its high performance. High efficiency light extraction was obtained by adopting backside emission architecture together with surface roughening treatment and TiO_2 anti-reflection coating. The fabricated AllnSb LED showed 75 % higher power conversion efficiency when compared with a commercially available device. The developed LED, together with a commercially available infrared (IR) detector equipped with band-pass optical filter (AK9710, manufactured by Asahi Kasei Microdevices) were coupled into a mirror system forming a light path length of 80 mm, which was tested for CO_2 gas sensing. For a non-absorbing environment, sensor output of 8 nA was obtained by driving the LED with peak current of 100 mA and, by exposing the system at CO_2 concentration of 1000 ppm signal reduction due to absorbance around 12% was obtained.