Enhanced performances of AlGaN/GaN HEMTs with dielectric engineering of HfZrO_x

III-nitrides based high electron-mobility transistors (HEMTs) are well-known excellent candidates for high-power, radio-frequency (rf) and high-temperature applications. However, HEMTs have to face the essential issues of high gate leakage current and drain current collapse (gate-lag), which inevitably limits the device performances and reliability. Here, we fabricate an optimized AlGaN/GaN metal-oxide-semiconductor high electron mobility transistor (MOS-HEMT), by using HfZrO_x (HZO) as a gate dielectric, that can improve the interfacial and transport properties. Compared to the conventional high permittivity (high-κ) gate dielectric HfO₂ which has attracted wide attention in recent years, the concentrations of interface traps and the inside fixed oxide defects are obviously reduced by using high quality HZO layer. Through the dielectric engineering of HZO, the MOS-HEMT with HZO dielectric shows an enhanced DC output performance with an increase of 54% at the optimal working condition, which is indeed much higher than that of the HfO₂ MOS-HEMT (40%). And the HZO MOS-HEMT exhibits a higher I_on/I_off ratio of 10⁶, an excellent subthreshold swing (SS) of 85 mV/decade, and a higher voltage swing (GVS). The gate leakage is reduced by nearly 8 orders of magnitude compared to the conventional unpassivated HEMTs (conv. HEMT) at the gate voltage of −5 V. These results are mainly caused by the replacement of the low-height Schottky barrier (SB) and the reduction of interface traps density. In order to further investigate the interfacial and electric properties of HZO MOS-HEMT, the dynamic gate/drain voltage and high-frequency capacitance-voltage (C–V) measurements are both applied. Remarkably, no measurable current collapse and C–V hysteresis are clearly observed, showing the enhanced interfacial and electric performances of the MOS-HEMT with dielectric engineering of HZO.