We study the use of a BGaN back-barrier layer in the GaN buffer of
AlyGa1−yN/GaN highelectron mobility
transistors to improve confinement of carriers in the 2D electron gas region.
Unlike InGaN back-barrier designs, whose polarization-induced sheet charges form
an electrostatic barrier at the backbarrier/ buffer interface, BGaN back-barrier
designs create an electrostatic barrier at the channel/backbarrier interface.
This can result in carrier confinement to sub-15 nm thickness, even when the
channel is 30 nm wide. Although polarization sheet charges due to the BGaN
back-barrier form a secondary well at the back-barrier/buffer interface,
increasing the thickness of the back-barrier may move the secondary well so that
it no longer interacts with the primary channel.