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

Enhancement of breakdown voltage (BV) with the increase of AlN buffer layer thickness was observed in AlGaNGaN high-electron-mobility transistors (HEMTs) grown by metalorganic chemical vapor deposition on 4 in. Si. The enhancement of device performance with AlN buffer thickness (200 and 300 nm) 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 200 μm wide HEMTs with 300 nm thick AlN buffer layer when compared to HEMTs with 8 nm thick AlN buffer layer. The location of junction breakdown in the device was identified as GaNAlNSi interface. The measured specific on-resistance (Ron) values for 200 and 400 μm wide HEMTs with 300 nm thick buffer layers were 0.28 and 0.33 mΩ cm2, respectively. About an order of low Ron was observed when compared with the reported values. The AlGaNGaN HEMTs on 4 in. Si with thicker AlN buffer layers are suitable for high-power applications.