The effect of dielectric stress on the electrical characteristics of AlGaN/GaN heterostructure field-effect transistors (HFETs)

We present an experimental analysis on the effect of dielectric stress on the electrical characteristics of AlGaN/GaN HFETs. Issues such as maximum current (I_d-max), gate leakage and current collapse are presented. Different dielectric deposition conditions were used to vary the amount of stress induced on the wafer and the devices were measured before and after passivation. A striking feature observed was the strong dependence of I_d-max on the amount of stress induced by the dielectric. I_d-max increases when the stress is tensile and reduces when it is compressive. The rise in leakage current was found to be dependent on the dielectric film itself and not on the stress induced, which suggests that a surface effect is responsible for the leakage mechanism.