AlGaN/GaN Metal–Oxide–Semiconductor Heterojunction Field-Effect Transistor Integrated With Clamp Circuit to Enable Normally-Off Operation

We have developed an AlGaN/GaN-on-Si metal- oxide-semiconductor heterojunction field-effect transistor (MOSHFET) integrated with a clamp circuit to enable normally-off operation. A clamp circuit consisting of a multilayer MIM capacitor and a Schottky barrier diode was monolithically integrated with a normally ON AlGaN/GaN MOSHFET. The integrated clamp circuit shifted the input driving signal from (0, 20 V) to (-19.2, 0.8 V), allowing the normally ON AlGaN/GaN MOSHFET with a pinchoff voltage of -14 V to be operated as a normally-off device. The multichannel device with a 5-mm channel width exhibited a drain current density of ~470 mA/mm and a breakdown voltage of 900 V. In comparison with other conventional normally-off GaN-based FETs, a higher threshold voltage with high current density (i.e., low ON-resistance) can be achieved with easy device processing, no need for gate recess or complicated epitaxial growth.