In this paper, we report the performance of room temperature operated mid-infrared light emitting diode (LED) with an InSb buffer layer and AlInSb 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<sub>2</sub> anti-reflection coating. The fabricated AlInSb 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<sub>2</sub> 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<sub>2</sub> concentration of 1000 ppm signal reduction due to absorbance around 12% was obtained.
This paper reports the development of a novel InSb infrared photovoltaic sensor (PVS) operating at room temperature. The PVS consists of an InSb p+p−n+ structure grown on semi-insulating GaAs(100) substrate, with a p+-Al0.17In0.83Sb barrier layer between the p+ and p− layers to reduce diffusion of photoexcited electrons. Photodiodes were fabricated by wet etching, and, using a 500-K blackbody, we obtained detectivity D*=2.8×108 cm Hz1/2/W and responsivity RV=1.9 kV/W at room temperature. The SNR was improved with the serial connection of 700 photodiodes patterned on a 600×600-µm2 chip. On increasing the number N of connected photodiodes, the SNR was improved by a factor of N1/2. The responsivity was constant for signals ranging from dc to 500 Hz. From spectral response measurements a cutoff wavelength of 6.8 µm was obtained. The PVS was flip-chip bonded on pre-amplifier IC, allowing the shortest possible connection between the PVS and the pre-amplifier, making the system immune to electromagnetic noise. The system was finally encapsulated in a dual flat nonleaded package with a window, which exposes the back of the GaAs substrate, allowing the infrared light incidence. The device is small (2.2×2.7×0.7 mm3), operates at room temperature, and is able to detect human body radiation in the middle IR range.
This paper reports the development of a novel InSb photovoltaic infrared sensor (InSb PVS) operating at room temperature. The InSb PVS consists of an InSb p<sup>+</sup>/p<sup>-</sup>/n<sup>+</sup> structure grown on semi-insulating GaAs (100) substrate, with a p<sup>+</sup> Al<sub>0.17</sub>In<sub>0.83</sub>Sb barrier layer between p<sup>+</sup> and p<sup>-</sup> layers to reduce diffusion of photo-excited electrons. Photodiodes were fabricated by wet etching process and, using a 500K blackbody, we obtained D* of 2.8x10<sup>8</sup> cmHz<sup>1/2</sup>/W and R<sub>V</sub> of 1.9 kV/W at room temperature. S/N was improved with the serial connection of 700 photodiodes patterned on a 600x600 μm<sup>2</sup> chip. Increasing the number (N) of connected photodiodes, S/N ratio was improved by a factor of N<sup>1/2</sup>. RV was constant for signals ranging from DC to 500Hz. From spectral response measurements a cut-off wavelength of 6.8 μm was obtained. The InSb PVS was flip-chip bonded on a pre-amplifier IC, allowing the shortest connection between the InSb PVS and the pre-amplifier, making the system immune to electromagnetic noise. The system was finally encapsulated by a Dual Flat Non-leaded (DFN) package with a window, which exposes the backside of the GaAs substrate allowing the infrared light incidence. The device external sizes are 2.2 mm x 2.7 mm x 0.7 mm and to our knowledge is the smallest uncooled sensor for the middle-infrared range reported until now.