Epitaxial oxide high electron mobility transistor

A high electron mobility transistor (HEMT), comprising:

• a substrate;
• a channel layer comprising a first epitaxial semiconductor layer on the substrate, the first epitaxial semiconductor layer comprising a first polar oxide material, wherein the first polar oxide material comprises an orthorhombic, tetragonal or trigonal crystal symmetry;
• a gate layer comprising a second epitaxial semiconductor layer on the first epitaxial semiconductor layer, the second epitaxial semiconductor layer comprising a second polar oxide material;
• a source electrode and a drain electrode coupled to the channel layer;
• a gate electrode coupled to the gate layer,
• wherein the first polar oxide material and the second polar oxide material comprise cation-polar surfaces oriented away from the substrate,
• wherein the second polar oxide material comprises a wider bandgap than the first polar oxide material,
• wherein the first epitaxial semiconductor layer comprises a 2-dimensional electron gas, and
• wherein the channel layer comprises a first superlattice comprising a plurality of first unit cells, wherein each of the first unit cells comprises a first sublayer comprising the first polar oxide material and a second sublayer.