Normally-off AlGaN/GaN heterojunction field-effect transistors with in-situ AlN gate insulator

AlGaN/GaN heterojunction field-effect transistors(HFETs)with p-GaN cap layer are developed for normally-off operation,in which an in-situ grown AlN layer is utilized as the gate insulator.Compared with the SiNxgate insulator,the AlN/p-GaN interface presents a more obvious energy band bending and a wider depletion region,which helps to positively shift the threshold voltage.In addition,the relatively large conduction band offset of AlN/p-GaN is beneficial to suppress the gate leakage current and enhance the gate breakdown voltage.Owing to the introduction of AlN layer,normally-off p-GaN capped AlGaN/GaN HFET with a threshold voltage of 4 V and a gate swing of 13 V is realized.Furthermore,the field-effect mobility is approximately 1500 cm^(2)·V^(-1)·s^(-1)in the 2DEG channel,implying a good device performance.

Hybrid-anode structure designed for a high-performance quasi-vertical GaN Schottky barrier diode

A quasi-vertical Ga N Schottky barrier diode with a hybrid anode structure is proposed to trade off the on-resistance and the breakdown voltage.By inserting a Si N dielectric between the anode metal with a relatively small length,it suppresses the electric field crowding effect without presenting an obvious effect on the forward characteristics.The enhanced breakdown voltage is ascribed to the charge-coupling effect between the insulation dielectric layer and Ga N.On the other hand,the current density is decreased beneath the dielectric layer with the increasing length of the Si N,resulting in a high on-resistance.Furthermore,the introduction of the field plate on the side wall forms an metal-oxide-semiconductor(MOS)channel and decreases the series resistance,but also shows an obvious electric field crowding effect at the bottom of the mesa due to the quasi-vertical structure.