High gain optical detection with GaAs field effect transistors

The photoresponse of GaAs field effect transistor (FET) optical detectors to optical intensity modulation signals of moderate frequency is investigated. High ac responsivity is available at frequencies of interest in optical communications: more than 6 A/W can be obtained up to 100 MHz, with a noise equivalent power of <10(-12) W/ radicalHz. The slope of the frequency response is dependent on the otpical bias power, an effect that can be attributed to traps. The GaAs FET optical detector complements the performance of available P-I-N and avalanche photodiode photodetectors for communications by providing high photoresponse at low bias voltages.