NOVELTY - The photodetector (520) has a reverse biasing circuitry applying voltage between cathode and anode regions such that cathode region is driven to high positive voltage than the anode region. A microstructure-enhanced photon absorbing semiconductor region is associated with the cathode and anode regions, and absorbs photons from a source signal. The absorbing region comprises a set of microstructures to increase absorption of photons at a range of wavelengths that includes a wavelength of the source signal relative to an absorbing region that is not intentionally microstructure-enhanced.    USE - Photodetector such as silicon photodiode, avalanche photodiode, photovoltaic device (all claimed) e.g. photovoltaic or solar cell, top illuminated microstructered PIN silicon photodiode and bottom illuminated microstructered NIP silicon photodiode for use in optical receivers of a fiber-optic communication system.    ADVANTAGE - The photodetector has microstructure enhanced absorption characteristics, and can be provided with a set of buried voids that is configured to increase lateral path length for increasing lateral electrical resistivity and decrease lateral thermal conduction for microwave transmission lines and/or thermal management in a pattern, so that vertical electrical and thermal conductance can be enhanced to form a conducting channel and quantum efficiency (QE) and operating wavelength range of the photodetector can be improved. The microstructures can be positioned to conduct heat from heat generating device to a heat sink so as to reduce thermal cross talk with other heat sensitive devices mounted on intermediate material.    DETAILED DESCRIPTION - The microstructure-enhanced photon absorbing semiconductor region and the microstructures are made of silicon, germanium and lll-V family material that is selected from a group consisting of indium phosphide, gallium arsenide, Indium gallium arsenide, gallium nitride, indium gallium nitride, indium gallium arsenide phosphide, aluminum gallium arsenide, Aluminum gallium nitride, gallium phosphide, indium antimonide and indium arsenide. INDEPENDENT CLAIMS are also included for the following:    (1) a microwave transmission line structure    (2) a optical waveguide structure    (3) a heat exchanger system.    DESCRIPTION OF DRAWING(S) - The drawing shows a cross section view of a top illuminated microstructered PIN silicon photodiode.    Photodetector (520)    Holes (522)    Pillars (524)    P-ohmic bond contact metal (528)    N-ohmic bond contact metal (530)