No abstract

A normally-off FET is necessary for switching devices. We report on the enhancement operation GaNbased heterojunction field effect transistors (HFETs). The AlGaN/AlN/GaN heterostructure on a Si (111) substrate was grown using a metalorganic chemical vapor deposition (MOCVD). The HFET for a normally-off operation was fabricated using the AlGaN/C-GaN heterostructure. As a result, the HFET was operated at the condition of the positive gate bias. The breakdown voltage of FET was over 350 V. The onstate resistance (R on ) was about 10 mohmcm 2 . The maximum operation current of the FET was over 10 A. We also confirmed that the normally-off HFET was operated at 573 K. The normally-off operation of AlGaN/GaN HFETs on the Si substrate was thus confirmed for the first time.

We demonstrate a novel field effect Schottky barrier diode (FESBD) with a dual Schottky structure combined with an AlGaN/GaN heterostructure to obtain a low on-voltage. The vertical and planar FESBDs were tried. A vertical AlGaN/GaN heterostructure was regrown by a selective area growth (SAG) technique using a metalorganic chemical vapor deposition (MOCVD). The contact layer was also grown using an SAG technique. Dual Schottky structures were fabricated to obtain a low on-voltage. That is, Al/Ti was used for a low Schottky barrier metal and Pt used for a higher barrier metal. The on-voltage of the diode was below 0.1 V. By the pinch-off effect of a higher Schottky barrier electrode, the reverse breakdown voltage was over 400 V although the Al/Ti used for a low Schottky barrier metal showed an ohmic property.