Mid-Infrared ${\rm Al}_{x}{\rm In}_{1-x}{\rm Sb}$ Light-Emitting Diodes and Photodiodes for Hydrocarbon Sensing

The properties of Al_xIn_1-xSb light-emitting diodes (LEDs) and photodetectors have been investigated to establish their suitability for methane sensing. Using these components it is possible to achieve good signal-to-noise values at both the characteristic absorption wavelength and also at 4 ¿m, an attractive wavelength for use as a reference channel. A limit of sensitivity of approximately 400 ppm, with an integration time of 10 s and a path length of 5 cm, was estimated for methane detection.