Analysis of electron trapping location in gated and ungated inverted-structure HEMT´s

Using gated (10-µm gate length) and ungated Inverted-Structure HEMT´s (GaAs/n-AlGaAs) with three microprobes, potential profiles along the channel were measured as a function of drain voltage VD. The gated FET was found to show the persistent enhancement of the channel resistance near drain region at VDof more than 1.5 V, on the other hand, the ungated FET showed it near source region at VDof more than 0.8 V, in the dark at 77 K. These effects are caused by the electron trapping in n-AlGaAs layers, and the intensity of electron trapping in the ungated FET was found to be stronger than that in the gated FET.