I–V and L–I characteristics as well as photocurrent in monolithic p‐InAsSbP/n‐InAs double heterostructure (λ = 3.4 μm) with several mesas/individual diodes grown onto a single n+‐InAs substrate have been measured at an activation of one of the diodes at ambient temperature in the presence of water, ethanol, and H20 + C2H5OH mixture at the n+‐InAs substrate surface. Adequately sufficient photocurrent values, the evidence for the absorption of internally reflected infrared radiation at the n+‐InAs substrate/liquid interface together with the correlation between the photocurrent and liquid chemical composition indicate the possibility of developing p‐InAsSbP/n‐InAs double heterostructures into a miniature monolithic “on‐chip” evanescent wave sensor of different liquids.

N-InAsSbP/InAs/P-InAsSbP double heterostructures have been grown onto n+-InAs substrate and further processed into 2×2 photodiode array containing no n+-InAs. C-V, spectral response as well as mid-IR photoluminescence and electroluminescence in the 77-300 K temperature range have been measured and used for photodiode characterization including D*(λ) and BLIP temperature evaluation.

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Narrow gap heterostructures consisting of two double heterostructures (N-InAsSbP/n-InAs/P-InAsSbP and P-InAsSbP/n-InAs0.9Sb0.1/N-InAsSbP) grown sequentially onto a n+-InAs substrate and further processed into a two-color photodiode with individual sensing operation at 3.3 and 4 have been studied. Presented and discussed are the photodiode construction details, I-V characteristics as well as sensitivity and detectivity spectra measured at room temperature.

We discuss photoelectrical properties of an on-chip attenuated total reflection (ATR) sensor for the ethanol concentration measurements in an aqueous solution. The on-chip sensor/microchip was made from a p-InAsSbP/n-InAs monolithic double heterostructure with three mesas/individual diodes grown on a single n+-InAs substrate/waveguide. Two heterostructure diodes were used as photodiodes, while the third one - as a LED. The ethanol concentration was measured via an algorithm based on analysis of the I-V characteristic parameters of a photodiode and the L-I characteristics of the LED. Keywords: photodiodes in the mid-IR range, LEDs in the mid-IR range, on-chip sensor, optical sensors, ATR sensor.