GaN on Si RF performance with different AlGaN back barrier

In this paper, the DC and RF device performance of AlGaN/GaN high-electron-mobility transistors (HEMTs) with different AlGaN back barrier thickness has been studied. The test results of the HEMTs with 50 nm back barrier exhibit
$\mathrm{I}_{\text{ds},\text{sat}}=640\ \text{mA}/\text{mm},\ \text{gm}=405\ \text{mS}/\text{mm}$
, and on/off ratio =
$1.5\mathrm{E}+04$
. In small-signal operation, cut-off frequency
$\mathrm{F}_{\mathrm{T}}/\mathrm{F}_{\text{MAX}}=59/127\ \text{GHz}$
are achieved, which gives a high value of
$(\mathrm{F}_{\mathrm{T}}\times\mathrm{L}_{\mathrm{g}})=14.7\ \text{GHz}\times\mu\mathrm{m}$
among the reported GaN-on-Si devices.