A novel normally-off GaN power tunnel junction FET

We demonstrate AlGaN/GaN tunnel junction FETs (TJ-FET) featuring a metal-2DEG Schottky junction at the source. The TJ-FETs exhibit normally-off operation in an otherwise normally-on as-grown sample owing to a current controlling scheme different from the conventional FETs. The high 2DEG density in AlGaN/GaN heterostructure results in a thin tunnel barrier whose effective thickness is controlled by an overlaying gate electrode. A positive gate bias results in a nanometer-thick barrier with high tunneling current, while a zero gate bias leads to a thicker barrier that effectively blocks the current flow. High drive current (326 mA/mm), low off-state leakage current (10−8 mA/mm) and high ION/IOFF ratio (1010) at a drain voltage of 50 V, and high off-state breakdown voltage (557 V) are obtained on a standard GaN-on-Si platform featuring a 1.8 μm buffer.