III-N transistor with an epitaxial layer providing a steep subthreshold swing

摘要

A III-N transistor having a steep subthreshold gradient and having an epitaxial semiconductor heterostructure is described. In embodiments, the III-N HFET employs a gate stack that is balanced and has opposing III-N polarization materials. For the opposing III-N polarization material, the overall effective polarization may be modulated by an external field, eg, related to the applied gate electrode voltage. In embodiments, the polarization strength difference between the III-N materials in the gate stack is adjusted by composition and / or film thickness to achieve the desired transistor threshold voltage (Vt). The polarization strength in the opposite gate stack is balanced with respect to each other, both forward and inverted gate voltage sweeps, where charge carriers are transferred to or from the III-N polarization layer and III-N channel semiconductor. When done, it can produce a sharp subthreshold swing in the drain current.