We report experimental results for the optical responsivity and noise-equivalent power (NEP) of quasi-optically coupled, room-temperature ErAs-InGaAlAs rectifier diodes. Four-micron-diameter diodes were flip-chip coupled to self-complementary log-periodic and square-spiral antennas, and characterized with a 104-GHz Gunn diode oscillator coupled to the rectifiers through variable attenuators, a feedhorn, an aspherical polymeric lens, and a Si hyperhemisphere. The log-periodic mounted device displayed a responsivity and specific NEP' of 0.9x10 3 V/W and 1.2x10 -12 W/Hz 1/2 , respectively. The square-spiral mounted device displayed a responsivity and NEP' of 1.2x10 3 V/W and 2.0x10 -12 W/Hz 1/2 , respectively. All values were measured at a post-detection center frequency of 33 Hz.