Creation of low-cost, portable sensors that can continuously provide information about the quality of the fuel for the tank is a very important task. Such sensors may be of interest both for car owners and manufacturers of automobile engines, as the life of an engine depends on fuel quality. One possible solution to this problem is the development of the infrared (IR) module to analyze the composition of gasoline and diesel fuel. In this paper transmission of IR radiation has been investigated in the range (1 - 4) $\mu m$ for petrol of different brands and motor-car diesel fuel. The most substantial distinctions in the IR radiation transmission have been identified.

$\href{https://pp.vk.me/c629114/v629114925/1293/R-ZPLZH5430.jpg}{Fig.~1.}$ Transmission spectra of gasoline (brand of the gasoline indicated on Fig.) and diesel fuel (dashed line).

Presence of light-emitting diodes and photodiodes with good operating parameters [1] is a necessary condition for creation of the smart IR module for the express analysis of petrol and diesel fuel. Previously we reported about creation of high-efficiency light-emitting diodes based on GaSb and InAs operating in the IR range [2, 3]. For the purpose specified above the photodiodes operating in the range of 2.0-3.6 $\mu m$ at the temperatures up to 60 $^\circ$C with the sensible area of 0.5 mm radius were developed. Two layers were deposited on the n-InAs substrate by the method of metalorganic vapour phase epitaxy. The active area of n-InAs was 2.5 $\mu m$ thick and the barrier layer of p-InAsSbP was 1.5 $\mu m$ in thickness with the using of Zn-containing source diethylzinc for p-n junction creation.For the improvement of operating parameters of photodiods the decline of concentration of charge carriers is needed in an active area, that was provided by the charge carriers compensation as diffusion of the acceptor impurity (Zn) proceeds. It was found out that distribution of concentration inside of the active area and of p-n junction position were influenced on the flux of diethylzinc which was varied within 0.20 $\mu$mol/min to 0.27 $\mu$mol/min. Experimentally C-U characteristics were measured at room temperature. The effective concentration of carriers in an active area was determined on the basis of the sharply asymmetrical p-n transition model. As the result the optimal growth conditions have been found from the point of view of flux value of diethylzinc FDeZn, namely: minimum concentration of charge carriers as much as $2.2\times 10^{16}~cm^3$ was obtained at FDeZn = 0.27 $\mu$mol/min. Thus the best operating parameters of photodiods were provided: responsivity R = 1.5 A/W, resistivity (at no bias) Ro = 1.1 kOhm, detectivity $D^*=1.6\times 10^{10} ~cm\sqrt{Hz}/W$, dark currents I = 60 $\mu$A (at reverse bias 100 mV), capacity C = 0.6 nF.

Summarizing, in this work investigations have been carried out which were necessary for creation of the smart IR module with the purpose of express analysis of motor-car fuel, namely: 1) Transmission spectra for motor-car diesel fuel and petrols in the middle IR range have been obtained; 2) Epitaxial layers growth conditions have been optimized for improvement of photodiode operating parameters.

References

1. $\href{http://www.lmsnt.com}{www.lmsnt.com}$.
2. N.D. Stoyanov, B.E. Zhurtanov, A.P. Astakhova, A.N. Imenkov and Yu.P. Yakovlev, High-efficiency LEDs of 1.6-2.4 $\mu m$ spectral range for medical diagnostics and environment monitoring, Semiconductors, 37, 8, 971-984, 2003.
3. N. Stoyanov, Kh. Salikhov , K. Kalinina, B. Zhurtanov, S. Kizhaev, Middle infrared LEDs: key element for new generation chemical sensors, Proceedings of the SPIE, 8257, 82571E-6, 2012.

LED Mictosensor NT, LLC, 26 Polytechnicheskaya str., Saint Petersburg, Russian Federation

National Mineral Resources University (Mining University), Saint Petersburg, Russian Federation