We report photomixer devices fabricated on a material consisting of self-assembled ErAs islands in GaAs, which is grown by molecular beam epitaxy. The devices perform comparably and provide an alternative to those made from low-temperature-grown GaAs. The photomixer's frequency response demonstrates that the material is a photoconductor with subpicosecond response time, in agreement with time-resolved differential reflectance measurements. The material also provides the other needed properties

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... uch as high photocarrier mobility and high breakdown field, which exceeds 2 ϫ10 5 V/cm. The maximum output power before device failure at frequencies of 1 THz was of order 0.1 W. This material has the potential to allow engineering of key photomixer properties such as the response time and dark resistance.