Infrared optical detectors operating in the 1.7- to 3-µm range based on lnxGa1−xSb for environmental gas-sensing

Devices operating in the 2-5 µm region are of potential importance for use in environmental sensing applications. Atmospheric pollutants such as CO, SOx, and NOx show absorption bands in the 2-5 µm range and passing any of these between a light source and detector will show a change in the detector signal. Strain-balanced GaSb/GaxIn1−xSb quantum well structures are being investigated to cover the 2-3 µm region grown on relaxed GaxIn1_xSb buffer layers. These provide low-strain structures while engineering the bandgap to realise the wavelength of interest. This paper is concerned mainly with the detector structure rather than the design of the active region. Hence bulk GaSb is used as the active region in some of the devices designed to ascertain the efficiency and sensitivity enhancement achievable from resonant structures.