GaAs Schottky diodes are analyzed as upper-mm-wave or THz direct-detectors in passive imaging arrays. Standard models are used for the current-voltage curve and small-signal responsivity with an assumed ideality factor of 1.2. The 1/f and burst noise properties are adopted from available empirical data, and a small-signal circuit model is used to compute the power delivered by the antenna to the diode. For a 4 sq mum diode area and typical modulation frequencies up to about 100 Hz, the noise-equivalent power (NEP) is found to be limited primarily by the 1/f and burst noise to values above similar to1 x 10(-10) W/Hz(1/2). If the modulation frequency could be increased to similar to1 MHz or above, or if the 1/f and burst noise mechanism could be greatly reduced, the analysis predicts that the Schottky NEP would drop to similar to3 x 10(-12) W/Hz(1/2) at room temperature. At video sampling rates (30 s(-1)), the corresponding noise-equivalent delta temperature (NEDeltaT) would fall in the range 1-10 K depending on the RF bandwidth. (C) 2004 Elsevier Ltd. All rights reserved.