Effect of optical phonon scattering on the performance limits of ultrafast GaN transistors

We investigate the intrinsic performance limits of GaN HEMTs by incorporating the effect of polar optical phonon backscattering into a quasi-ballistic model. Then, we include parasitic elements and quantitatively investigate the degradation in performance. The method used is semi-analytical, and will prove very helpful in designing future generations of devices. The work not only sets a roadmap for scaling to high speeds, it also offers clear physical reasons for a number of unexplained features observed in state-of-the-art GaN HEMTs.