Performance of GaN MESFETs with an undoped highly resistive buffer layer

In this paper, we report on the DC and RF performances of recessed gate GaN MESFETs fabricated using an undoped highly resistive buffer layer. The performance of the device is found to be significantly improved compared with that of a device with an Mg-doped p^--GaN buffer layer. The performance improvement stems from the resistance of an undoped layer being higher than that of a p^--GaN buffer layer. The GaN MESFET fabricated with an undoped highly resistive layer exhibits a current saturation at V_DS = 4 V and V_GS = 0 V and a pinch-off at V_GS = -3 V. The peak drain currents of the device are about 230 mA/mm and 215 mA/mm at 300 K and 473 K, respectively. The room temperature f_T and f_max from the device are 6.35 GHz and 10.25 GHz, respectively. A physics-based analytic model was applied and found to be useful for predicting the DC performance of the GaN MESFET.