ALN Barrier with High Sheet Carrier Density for High Power Application

Abstract

The Aluminium gallium nitride (AlGaN) has a wide band gap and large polarization charge which result in high carrier density even when using ultrathin barrier layers, Al-rich-barrier GaN-based high-electron-mobility transistors (HEMTs) are of increasing interest. For instance, it has been demonstrated that In0.19Al0.81N/GaN or AlN/GaN HEMTs could be an alternative to the commonly used AlGaN/GaN heterostructure for high-frequency and high-power GaN-based applications. Ultrathin-barrier normally off AlN/GaN/AlGaN double-heterostructure field-effect transistors using an in situ SiN cap layer have been fabricated on 100-mm Si substrates for the first time. The high 2DEG density in combination with an extremely thin barrier layer leads to enhancement-mode devices with state-of-the-art combination of specific ON-resistance that is low and breakdown voltage is high at zero biasing voltage. Despite the 2-μm gate length used, the transconductance peaks high. Furthermore, pulsed measurements show that the devices are dispersion free up to high drain voltage VDS. More than 200 devices have been characterized in order to confirm the reproducibility of the results. Power switching devices could also benefit from an ultrathin Al-rich barrier material.