Investigation of GaN channel thickness on the channel mobility in AlGaN/GaN HEMTs grown on sapphire substrate

We have invented a novel channel mobility extraction method in the gated region of AlGaN/GaN high-electron-mobility transistors (HEMTs). The resistances in the contact, gated, and access region were extracted from Id(Vg) measurements on a set of HEMTs with various gate-to-drain distances and gate lengths. By considering the impact of the access and contact resistances, an accurate model to describe the channel mobility behavior in the gated region has been achieved. This channel mobility extraction method has been employed for different GaN channel thickness devices to study the effect of the GaN channel thickness on the device performance. Our systematic measurements have revealed that the channel mobility increases up to a certain channel thickness due to the reduced edge-type dislocation density evidenced by the X-ray diffraction measurement data.