Low Static and Dynamic On‐Resistance with High Figure of Merit in AlGaN/GaN High Electron Mobility Transistors on Chemical Vapor Deposited Diamond

AlGaN/GaN high electron mobility transistors (HEMTs) on chemical vapor deposited (CVD) diamond with different gate–drain spacings ( L gd ) are fabricated, and off‐state breakdown voltage (BV gd ) along with a dynamic specific on‐resistance (Dyn.‐ R on,sp ) is measured. R on,sp is obtained in the range of 0.32–0.98 mΩ cm 2 for HEMTs with L gd of 2–8 μm. The HEMTs exhibit a BV gd of 415 V ( L gd  = 8 μm) with a maximum lateral breakdown strength of 0.72 MV cm −1 . The power device figure of merit (FOM) of ≈0.18 GW cm −2 is obtained from HEMTs with L gd of 8 μm. The HEMTs exhibit about 60% of higher FOM when compared with the reported HEMTs on CVD diamond (≈0.11 GW cm −2 ). This is mainly due to the improvement of R on,sp through the reduction of contact resistance ( R c ) and sheet resistance ( R sh ). The Dyn.‐ R on,sp is estimated from pulsed (pulse width/period = 200 ns/1 ms) I D – V D characteristics, which is comparable with the static R on,sp . These improved results of the fabricated AlGaN/GaN HEMTs on CVD diamond make it a promising candidate for high‐voltage power switching device applications.