Інститут фізики напівпровідників ім. В.Є. Лашкарьова НАН України
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Sensors based on 2D macroporous silicon structures with surface-active nanocoatings

№20 Department of photonic semiconductor structures
L.A. Karachevtseva, F.F. Sizov, Yu.V. Goltvyansky , K.P. Konin, O.J. Stronska , K.A. Parshin , O.A. Lytvynenko

014 014 2 
Fig.1. Micrograph of macroporous silicon
structures with nanocoatings SiC (а) and microtubes SiC (b).
           а                                                 b  
014 3 014 4
Рис. 2а
Short-wavelength spectral dependencies of photoresponse of silicon monocrystal (1) and macroporous silicon structures with SiO2 nanocoatings (2, 3, 4).		 Рис. 2b
Spectral dependences of photoconductivity and absorption of macroporous silicon structure with SiO2 nanocoating.

Macroporous silicon fabricated by a method of photoanodic etching, takes a special place among 2D photonic structures. It is connected to an opportunity of manufacturing of structures with necessary geometry, formation of additional optical absorption bands, its photoelectrical properties. Progress in the nanotechnology allows realizing new photonic and optoelectronic silicon devices.

Basic physical phenomenon that determines promising of 2D macroporous silicon structures as sensor elements is the amplification of absorption of electromagnetic radiation, photoconductivity and Raman scattering as a result of the optical mode interaction with a
cylindrical macropore surface. It opens possibilities of development compact uncooled photosensors at the wavelengths in of indirect silicon zone - zoned transition, thermal and biosensors. Additional functionalities of 2D macroporous silicon structures are connected with hetero junction on the "nanocoating-silicon" boundary on a macropore surface, with radiating complex microporous-macroporous silicon structures and at use of macroporous silicon as a matrix for the microtube formation.

Photoreceiving structure with macroporous silicon layer shows responsivity 3 A/W and detectivity D*λ = 1010 W-1cm×Hz-1/2 for λ≈0.5÷1 micron that corresponds to the best parameters of PIN-photodiodes. The increase in absorption in near infrared spectral provides detectivity of bolometric elements on the basis of structures of macroporous silicon up to D* λ≈109 W-1cm×Hz-1/2. Structures of 2D macroporous silicon structures are sensitive in area 1.2-1.4 micron that opens opportunities to registration "singlet-triplet" transition of the excited oxygen at wavelength 1.27 micron. Photoconductivity was measured in a wide range from 0.4 microns up to 4 microns on macroporous silicon structures with nanocoatings SiO2, microporous silicon and SiC obtained by the method of low temperature gas transport reactions. Radiating complex microporous-macroporous silicon structures can be used as sensor controlled the local centers on a macropore surface, which photoluminescence parameters depend by the nature of local centers. Microtubes on a macropore surface as a result of oxidation or SiC nanocoating formation are perspective for the liquid control.

The increase in absorption in near-infrared spectral area as a result of the impurity Frantz-Keldysh’s effect provides detectivity of bolometric elements on the basis of structures of macroporous silicon, which surpass characteristics of analogues. It was established that for macroporous silicon structures with heterojunction on the "nanosoating-silicon" boundary on a macropore surface the photoresponse is realized under the conditions of carrier transport through a surface barrier that essentially expands a range of photosensitivity in dependence by nature surface-active nanocoatings.

Karachevtseva L.A., Sizov F.F., Goltvyansky Yu.V., Konin K.P., Stronska O.J., Parshin K.A., Lytvynenko O.A., UA Patent “Uncooled Thermosensitive Element for Bolometers”, № 80345 (10.09.2007).
Karachevtseva L.A., Glushko A.E., "Two-dimensional photonic crystal ", the patent application, a-2006, № 10576.