Study of gate leakage current on AlGaN/GaN MOS-HEMTs with atomic layer deposited Al₂O₃ gate oxide

We have investigated the current transport mechanism of both the reverse and forward gate leakage currents in Au/Ni/Al₂O₃/AlGaN/GaN metal-oxide-semiconductor high electron mobility transistors (MOSHEMTs) with the current-voltage (I–V) characteristics in the temperature range of 300– 400 K. The room temperature capacitance-voltage (C–V) characteristics revealed a two-step capacitance change, which is the characteristic feature of the MOS-HEMT structure having two interfaces. An analysis of reverse gate leakage current of the Au/Ni/Al₂O₃/AlGaN/GaN MOS structure indicated the dominance of Poole-Frenkel emission mechanism and Schottky emission mechanism in the lower and higher bias regions, regardless of the temperature. The forward log I–log V plot of the Au/Ni/Al₂O₃/AlGaN/GaN MOS structure exhibited two different regions having different slopes, implying the domination of different conduction mechanisms in each region. At higher forward bias, the space-charge-limited current conduction mechanism dominated the current transport indicating the presence of traps with most of the traps being deep traps with trap energy E_t » 0.17 eV as determined from the plot of exponent m versus the reciprocal of temperature.