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 V
D
. The gated FET was found to show the persistent enhancement of the channel resistance near drain region at V
D
of more than 1.5 V, on the other hand, the ungated FET showed it near source region at V
D
of 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.