Integrated enhancement/depletion‐mode GaN MIS‐HEMTs for high‐speed mixed‐signal applications

Abstract

Monolithically integrated enhancement/depletion (E/D)‐mode AlGaN/GaN metal–insulator–semiconductor high electron mobility transistors (MIS‐HEMTs) are being developed for high‐speed mixed‐signal applications. Partially recessed gate combined with buffered gate insulator produce remarkably improved trade‐off between the threshold voltage (1.4 V) and current density (848 mA mm−1) in the E‐mode device. Record peak transconductances of 311 and 248 mA mm−1 are obtained for D‐ and E‐mode MIS‐HEMTs, respectively. A direct‐coupled FET logic (DCFL) 51‐stage ring oscillator implemented using the MIS‐HEMT technique is fabricated, which exhibits high‐speed performance with an oscillation frequency of 908 MHz and a high output voltage swing of 1.48 V.