Normally-off AlGaN/GaN power tunnel-junction FETs

We present normally-off AlGaN/Gan power tunnel-junction FETs (TJ-FETs) with high breakdown voltage, low off-state leakage current and low specific on-resistance. 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. This tunnel junction is controlled by an overlapping gate and deliver highly efficient quantum tunnelling, enabling normally-off operation. A positive gate bias results in a nanometer-thick barrier with high tunnelling current, while a zero gate bias leads to a thicker barrier that effectively blocks the current flow. High tunnel current (326 mA/mm), low off-state leakage (10^-8 mA/mm) and high off-state breakdown voltage (557 V) are obtained on a standard GaN-on-Si platform featuring a 1.8 μm buffer. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)