Microwave performance of AlGaN/GaN high electron mobility transistors on Si(111) substrates

The first AlGaN/GaN high electron mobility transistors (HEMTs) on silicon substrates have been realized using Organometallic Vapor Phase Epitaxy (OMVPE). Static output characteristics with low output conductance and isolation approaching 80 V were observed on devices fabricated on 1 /spl Omega/-cm p-Si(111). At microwave frequencies, a capacitively coupled substrate charge limits the device performance, resulting in a 25 GHz cutoff frequency and 0.5 W/mm output power for 0.3 /spl mu/m gate length devices. A small-signal equivalent circuit incorporating elements representing the parasitic loading from the substrate accurately models the capacitive coupling effect observed on measured S-parameters.