NOVELTY - A method of controlling thermal conductivity and thermoelectric power of a material while maintaining electrical conductivity of the material, involves providing semiconductor nanowires as the material; controlling the thermal conductivity of the nanowires independently of their electrical conductivity by controlling dimensions of the nanowires; and controlling the thermoelectric power of the nanowires independently of their electrical conductivity by controlling doping of the semiconductor nanowires.    USE - For controlling thermal conductivity and thermoelectric power of a material while maintaining electrical conductivity of the material useful for power generation; and to fabricate alternately p-doped and n-doped arrays of silicon nanowires.    ADVANTAGE - The method takes advantage of phonon drag effects. The method provide for the fabrication of thermoelectric nanowire devices with ZT values greater than or equal to 1; allows for thermoelectric nanowire devices to be made from a broad class of semiconductor materials. These semiconductors allow for control of their doping level so that the three thermoelectric material parameters can be precisely controlled. The method also provides the fabrication of vertically standing p- and n-type semiconductor nanowires connected electrically in series and thermally in parallel.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) thermoelectric device comprising p-doped and n-doped semiconductor nanowire thermocouples, the p-doped and n-doped semiconductor nanowire thermocouples being connected electrically in series and thermally in parallel;    (2) method to fabricate alternately p-doped and n-doped arrays of silicon nanowires, involving providing a silicon-on-insulator (SOI) substrate; insulating a top silicon layer of the SOI substrate; coating the insulated top silicon layer with photoresist; patterning the photoresist into a series of isolated, alternately p-doped and n-doped, regions separated by insulator; removing the insulator between the isolated regions; etching separation regions under the removed insulator up to an insulator layer of the SOI substrate; removing the photoresist; patterning circles on top of each isolated region; etching the isolated regions, the circles for each isolated region acting as a mask, to obtain, for each isolated region, a nanowire array comprising nanowires having same diameter as the circles.