Structure dependence of the short‐channel effect in GaAs MESFETs. Two‐dimensional device simulation

Abstract

AbstractThe structure dependence of the short‐channel effect in GaAs MESFETs has been investigated using a two‐dimensional device simulator. The short‐channel effect for 1‐μm gate length has been clarified as being due to the decrease in the potential barrier at the substrate region under the channel, especially toward the source. This decrease in the potential barrier increases the current injection into the substrate under the channel, and causes the threshold voltage and a decrease in the K value, which is one of the performance criteria of FETs. A structure with a thin source/drain n+ layer, an offset structure with a small spacing between the gate electrode and the n+ layer, and an LDD structure with an intermediately doped layer between the gate and the n+ layer increase the potential barrier effect in the substrate compared to a conventional self‐aligned structure, thereby reducing the short‐channel effect. In addition, the formation of a p‐layer around the n+ layer increases further this effect, resulting in an almost short‐channel affect free FET action down to 1–μ gate length.