Investigation of Pd|HfO$_2$|AlGaN|GaN enhancement-mode high electron mobility transistor with sensitization, activation, and electroless-plating approaches

A new Pd|HfO$_2$|AlGaN|GaN metal-oxide-semiconductor (MOS) enhancement-mode high electron mobility transistor (HEMT) is fabricated with low-temperature sensitization, activation, electroless-plating, and two-step gate-recess approaches. Experimentally, a high positive threshold voltage $V_{\mathrm{th}}$ of 1.96 V, a very low gate leakage $I_{\mathrm{G}}$ of 6.3 $\cdot$ 10$^{-8}$ mA/mm, a high maximum extrinsic transconductance gm,max of 75.3 mS/mm, a high maximum drain saturation current $I_{\mathrm{D,max}}$ of 266.9 mA/mm, and a high ON/OFF current ratio of 7.6 $\cdot$ 10$^7$ are obtained at 300 K. Moreover, the related temperature-dependent characteristics, over temperature ranges from 300 to 500 K, are comprehensively studied. The very low temperature coefficients on gate current, drain saturation current, transconductance, and threshold voltage confirm the thermal-stable capability of the studied device. Therefore, based on these advantages, the studied Pd|HfO$_2$|AlGaN|GaN MOS structure is suitable for the development of high-performance HEMTs.