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Two-dimensional photonic macroporous silicon structures

№20 Department of photonic semiconductor structures
L.A. Karachevtseva, O.A. Lytvynenko, A.E. Glushko

	Fig.1. Two-dimensional photonic macroporous silicon structures with periodic (a, b) and arbitrary (c) arrangement of cylindrical macropores respectively in 6, 2, 3 microns diameter and up to 250 microns depth.
a                                        b                                   c
	Fig.2. The scheme of macroporous silicon structures etching at presence of holes which generated by illumination of the back side of a silicon plate.

Two-dimensional photonic macroporous silicon structures (Fig. 1) - a perspective material for development of radiating, photo- and thermodetecting devices. It is connected to an opportunity of manufacturing of structures with necessary geometry due to crystal anisotropy which allows to use methods of plasmochemical etching, low temperature gas transport reactions and inexpensive process of photoelectrochemical etching. Devices based on two-dimensional photonic macroporous silicon structures can be used for needs of ecological environment monitoring, control in medicine and industry.

Two-dimensional macroporous silicon structures are formed by a method of photoelectrochemical etching of single crystal silicon (Fig. 2). Periodic arrangement of air cylindrical macropores has been provided with corresponding periodic accommodation of etching pits. The last have been preliminary generated as a result of photolithographic procedure and anisotropic etching. Structures with arbitrary arrangement of air cylindrical macropores have been generated without photolithographic procedure on неоднородностях a relief and distribution of impurity to surfaces of a plate of single crystal silicon. Formation of macropores occurs in conditions of the self-organized process of photoelectrochemical etching silicon n-type conductivity in a solution of a hydrofluoric acid. According to the circuit etchings (Fig. 2) the holes being minority carriers in silicon n-type conductivity, are generated by light on the back side of a sample and transferred by an electric field to border "silicon-electrolyte " where there passes reaction. The increased intensity of an electric field on the ends of pores results that holes transport occurs mainly in these places that determine a direction of cylindrical macropores formation.
Silicon oxide nanocoatings have been formed on a structures surface by methods of anodic oxidation, dry and damp oxidation; the nanocoating of a silicon carbide has been formed by a method of low temperature gas transport reactions.

Two-dimensional macroporous silicon structures have been made with a periodic and arbitrary arrangement of macropores in diameter Dp = 1-10 microns, depth up to H = 250 microns and concentration Np = (1.5-6)×10⁶ сm². Nanocoatings of silicon oxide up to 10 nanometers, 50 800 nanometers thickness have been generated on a surface of macropores; the nanocoatings of a silicon carbide had thickness up to 200 nanometers.

For formation of silicon macroporous structures on the basis of a silicon plate with any resistivity process of photoelectrochemical etching is advanced in view of influence volume recombination on holes transport for formation of in parallel located macropores. The three-component structure is developed on the basis of macroporous silicon with a nanocoating that allows realizing the maximal width of the photonic forbidden zone in the field of optical communication lengths of waves (1.55 microns) at preservation of durability of a photonic crystal.