Comparison of DC performance of Pt/Ti/Au- and Ni/Au-gated AlGaN/GaN high electron mobility transistors

We have demonstrated significant improvements of AlGaN/GaN high electron mobility transistors (HEMTs) dc performance by employing Pt/Ti/Au instead of the conventional Ni/Au gate metallization. During off-state bias stressing, the typical critical voltage for HEMTs with Ni/Au gate metallization was ∼-45 to -65 V. By sharp contrast, no critical voltage was observed for HEMTs with Pt/Ti/Au gate metallization, even up to -100 V, which was the instrumental limitation in this experiment. After the off-state stressing, the drain current of Ni/Au gated-HEMTs decreased by ∼15%. For the Pt-gate HEMTs, no degradation of the drain current occurred and there were minimal changes in the Schottky gate characteristics for both forward and reverse bias conditions. The HEMTs with Pt/Ti/Au metallization showed an excellent drain on/off current ratio of 1.56 × 10⁸. The on/off drain current ratio of Ni-gated HEMTs was dependent on the drain bias voltage and ranged from 1.16× 10⁷ at V_DS=5 V and 6.29× 10⁵ V _DS =40 V due to the larger gate leakage current at higher drain bias voltage.