Low leakage high breakdown e-mode GaN DHFET on Si by selective removal of in-situ grown Si3N4

We describe the fabrication and characteristics of high voltage enhancement mode SiN/AlGaN/GaN/AlGaN double heterostructure FET devices. The Si₃N₄ not only acts as a passivation layer but is crucial in the device concept as it acts as an electron donating layer (1). By selective removal under the gate of the in-situ SiN, we realize e-mode operation with a very narrow threshold voltage distribution with an average value of +475 mV and a standard deviation of only 15 mV. Compared to the reference depletion mode devices, we see no impact of the e-mode architecture on the breakdown behaviour. The devices maintain very low leakage currents even at drain biases up to 80% of the breakdown voltage.