Gate leakage mechanisms in normally off p-GaN/AlGaN/GaN high electron mobility transistors

In this letter, gate leakage mechanisms in different gate contact normally off p-GaN/AlGaN/GaN high electron mobility transistors (HEMTs) have been studied by the temperature-dependent current-voltage (IG-VG) measurement. It is found that two-dimensional variable range hopping is responsible for gate leakage current at the reverse gate bias and low forward gate bias in both high-leakage and low-leakage Schottky gate contact devices. At high forward gate bias, in the case of high-leakage Schottky contact, the dominant current conduction mechanism is found to be thermionic field emission while it is Poole–Frenkle emission (PFE) for the case of low-leakage Schottky contact and the activation energy of trap states for PFE current is derived as 0.6 eV. Besides, related models are also proposed to describe the gate leakage current in p-GaN gate HEMTs and they match well with the experimental gate leakage current within a wide range of temperatures and gate biases.