The photosensitivity of 50 and 100 μm square microdischarge devices having an inverted pyramidal Si cathode has been demonstrated and characterized in the ultraviolet, visible, and near-infrared (350–1200 nm). When operating with 500 Torr of Ne, (100 μm)2 microdischarge devices exhibit responsivities of 700±150 and 570±120 A W−1 at 850 and 660 nm, respectively, or more than an order of magnitude larger than peak values typical of commercially available Si avalanche photodiodes. Maximum sensitivity occurs in the 800–900 nm region for the larger (100 μm square) devices but is blueshifted to 600–650 nm for (50 μm)2 detectors. The peak response for the 50 μm square device is 950±250 A W−1 (at ∼625 nm), an increase of ∼35% over that for the (100 μm)2 detector. The experimental results indicate that the semiconductor photocathode determines the spectral response of the device whereas the plasma serves as an electron multiplier. The sensitivity and dynamic range of this new hybrid semiconductor/plasma photodetector suggest that arrays of microdischarge photodetectors are potentially valuable for spectroscopic and biochemical applications. © 2002 American Institute of Physics.