Optimizing indium aluminum antimonide LEDs and photodiodes for gas sensing applications

Harvey R. Hardaway; Tim Ashley; Louise Buckle; Martin T. Emeny; Graeme Masterton; Graham Pryce

doi:10.1117/12.560577

22 October 2004 Optimizing indium aluminum antimonide LEDs and photodiodes for gas sensing applications

Harvey R. Hardaway, Tim Ashley, Louise Buckle, Martin T. Emeny, Graeme Masterton, Graham Pryce

Proceedings Volume 5564, Infrared Detector Materials and Devices; (2004) https://doi.org/10.1117/12.560577
Event: Optical Science and Technology, the SPIE 49th Annual Meeting, 2004, Denver, Colorado, United States

Abstract

We have developed a range of un-cooled mid-IR LEDs and photodiodes for IR gas sensing applications. Varying the composition of MBE grown Indium Aluminium Antimonide (In_(1-x)Al_xSb) epi-layers on GaAs allows us to engineer the emission/detection wavelength for a particular gas up to λ_max≈6μm. The relatively high series resistance, LED drive requirements, and the non-optimised impedance matching of the un-biased photodiodes restricts the market for these components. Sub-dividing single element devices into N smaller devices connected in series enable the LED current and voltage requirements to be tailored to match the source, and improves the photodiode impedance matching. We report the development of the necessary growth and photolithography technologies for series-connecting InAlSb diodes on GaAs substrates. We include results from multi-element Co₂ (Al(x)=4.5%) and CH₄ (Al(x)=8.5%) sensing LEDs and photodiodes. These impedance matched LEDs represent a 9-fold improvement in the wall-plug efficiency compared with single element LEDs with the same light output. The impedance of the multi-element photodiodes is increased significantly with respect to the series resistance, which gives up to a 5-fold improvement in sensitivity since the noise contributions from the external amplifier and series resistance are minimised. These advances have greatly improved the suitability of these components for gas sensing, and further improvements in the performance are expected through optimisation of the epi-layer design and the device geometry.

Citation Download Citation

Harvey R. Hardaway, Tim Ashley, Louise Buckle, Martin T. Emeny, Graeme Masterton, and Graham Pryce "Optimizing indium aluminum antimonide LEDs and photodiodes for gas sensing applications", Proc. SPIE 5564, Infrared Detector Materials and Devices, (22 October 2004); https://doi.org/10.1117/12.560577

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