Light sensitivity of GaAs pHEMT´s: A close insight into the microwave noise behavior

The present work deals with experimental analysis and discussion of the light sensitivity of GaAs pseudomorphic HEMT´s to visible laser exposure from the viewpoint of microwave noise performance. A comparative study has been performed with respect to the layout of different devices having the same total gate width but different access layouts in terms of gate fingers and pitch. Significant differential effects have been brought to evidence either in the DC current characteristics and in the 2-26 GHz noise parameters F_min, Γ_opt and R_n markedly affected from light. A correlation has been found among the gate layout, increase of gate current under exposure and degradation of noise behavior.