AlN/GaN MIS-HEMT With GeN Gate Dielectric for mm-Wave Applications

In this work, a high-performance AlN/GaN metal–insulator–semiconductor high electron mobility transistor (MIS-HEMT) with germanium nitride (GeN) as a gate dielectric was fabricated. The gate dielectric was deposited using thermal evaporation and nitridation methods to prevent interface damage and fixed charges caused by plasma growth or sputtering. With the developed nitride-GeN dielectric, the MIS devices exhibit excellent electrical characteristics, including a negligible hysteresis of 0.05 V, a four-order reduction in gate leakage current, and an enhanced gate swing voltage. For a 150-nm gate length, the device achieved a maximum drain current density of 2.03A/mm and an effective current-gain cutoff frequency/maximum oscillation frequency ( $f_{\mathrm {T}}$ / $f_{\mathrm {MAX}}$ ) of 81/131 GHz. At 30 GHz, it delivered a remarkable power density of 3.9 W/mm at $V_{\mathrm {DS}} =12$ V in the CW mode. These promising results indicate that GeN could be a new and attractive gate dielectric option for AlN/GaN HEMTs functioning in the Ka-band frequency range.