A study on the negative photoresponse of AlGaAs/GaAs MODFETs

A model for the mechanism of negative photoresponse, i.e. the decrease of drain current under illumination, in AlGaAs/GaAs MODFETs (modulation-doped field--effect transistors) is presented. A comprehensive experimental study examining the dependence of this phenomena on gate-to-source bias voltage and optical power is also reported. The negative photoresponse is attributed to trapping of photogenerated carriers in the GaAs buffer layer, causing a change in the potential profile and a consequent reduction in the number of carriers in the 2-DEG (two-dimensional electron gas) channel.<
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