Experimental/numerical investigation of the physical mechanisms behind dc-to-RF dispersion effects in GaAs-based HFET´s

A consistent set of experimental and numerical results are presented, addressing to dc-to-RF dispersion effects in AlGaAs-GaAs heterostructure FET´s (HFET´s). Results are presented from gate-lag, transconductance (g^m) frequency dispersion and current deep level transient spectroscopy (I-DLTS) experiments, allowing consistent indications about energy and location of deep-level traps to be inferred. Experimental data are fully explained by numerical device simulations, pointing out that surface traps act differently from conventionally assumed, i.e. behave as hole traps interacting with holes attracted at the ungated surface by negatively-ionized levels and consequent band bending.