Evaluation of AlGaN/GaN metal–oxide–semicondutor high-electron mobility transistors with plasma-enhanced atomic layer deposition HfO2/AlN date dielectric for RF power applications

Abstract

A plasma enhanced atomic layer deposition (PEALD) HfO2/AlN dielectric stack was used as the gate dielectric for AlGaN/GaN metal–oxide–semiconductor high-electron-mobility transistors (MOS-HEMTs) for high-frequency power device applications. The capacitance–voltage (C–V) curves of the HfO2/AlN/GaN MOS capacitor (MOSCAP) showed a small frequency dispersion along with a very small hysteresis (∼50 mV). Moreover, the interface trap density (Dit) was calculated to be 2.7 × 1011 cm−2 V−1 s−1 at 150 °C. Using PEALD-AlN as the interfacial passivation layer (IPL), the drain current of the HfO2/AlN MOS-HEMTs increased by about 46% and the gate leakage current decreased by six orders of magnitude as compared with those of the conventional Schottky gate AlGaN/GaN HEMTs processed using the same epitaxial wafer. The 0.3-µm-gate-length HfO2/AlN/AlGaN/GaN MOS-HEMTs demonstrated a 2.88 W/mm output power, a 23 dB power gain, a 30.2% power-added efficiency at 2.4 GHz, and an improved device linearity as compared with the conventional AlGaN/GaN HEMTs. The third-order intercept point at the output (OIP3) of the MOS-HEMTs was 28.4 as compared with that of 26.5 for the conventional GaN HEMTs. Overall, the MOS-HEMTs with a HfO2/AlN gate stack showed good potential for high-linearity RF power device applications.