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 AlNbuffer layer thickness was observed in Al Ga N ∕ Ga N 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 μ m wide HEMTs with 300 nm thick AlNbuffer layer when compared to HEMTs with 8 nm thick AlNbuffer layer. The location of junction breakdown in the device was identified as Ga N ∕ Al N ∕ Si interface. The measured specific on-resistance ( R on ) values for 200 and 400 μ m wide HEMTs with 300 nm thick buffer layers were 0.28 and 0.33 m Ω cm 2 , respectively. About an order of low R on was observed when compared with the reported values. The Al Ga N ∕ Ga N HEMTs on 4 in. Si with thicker AlNbuffer layers are suitable for high-power applications.