Investigation of low frequency dependence of output conductance in GaAs MESFET

In this work, we experimentally investigate the effects of the extension of depletion regions in a GaAs MESFET on the frequency variation of the output conductance, gd, as well as the maximal relative variation, Δgdmax, at different polarisations of drain-source, Vds, and gate-source, Vgs. It is found that, for weak depleted regions, the values of gd(f) are very small with a Δgdmax which remains negligible. However, for large extensions, the values of gd(f) are very significant; they could reach 371.4 (omega)-1 together with a Δgdmax high value of about 2.7 dB at Vds = 1.5V and „ Vgs„  = 0.2V. Moreover, Δgdmax values undergo an increase when Vds increases. Hence, maximal variation of the dispersion gets higher when the re- gions become more depleted. Therefore, the widening of space charge region introduces frequency dispersion of gd that may limit potential GaAs MESFET applications in several fields in Micro- and nano-devices.