Enhancement of breakdown voltage by AlN buffer layer thickness in AlGaN∕GaN high-electron-mobility transistors on 4in. diameter silicon

Abstract

Enhancement of breakdown voltage (BV) with the increase of AlN buffer layer thickness was observed in AlGaN∕GaN high-electron-mobility transistors (HEMTs) grown by metalorganic chemical vapor deposition on 4in. Si. The enhancement of device performance with AlN buffer thickness (200 and 300nm) is due to the reduction of electrically active defects from Si substrate. The reduction of defects from Si with the increase of AlN thickness was confirmed by x-ray rocking curve measurements. Not much change has been observed in ON-state BV (BV:ON) values except in devices with 500-nm-thick buffer layer. About 46% enhancement in OFF-state BV (BV:OFF) was observed on 200μm wide HEMTs with 300nm thick AlN buffer layer when compared to HEMTs with 8nm thick AlN buffer layer. The location of junction breakdown in the device was identified as GaN∕AlN∕Si interface. The measured specific on-resistance (Ron) values for 200 and 400μm wide HEMTs with 300nm thick buffer layers were 0.28 and 0.33mΩcm2, respectively. About an order of low Ron was observed when compared with the reported values. The AlGaN∕GaN HEMTs on 4in. Si with thicker AlN buffer layers are suitable for high-power applications.